I agree that it's a bit too underrated. But it's not very useful either, and that's why it's frowned upon...
Still, I do thing it gets too much hatred. And those moves are all quite capable finishers. Yes. Most of the time, another move will work so much better. But there are certain scenarios where those Moves could be much more useful. I actually consider Frenzy Plant to be a quite nice alternative for Meganium. The move she'll use the most for attacking is Ancient Power, or even Counter. Her Grass Movepool is actually somewhat limited (Well, the WHOLE Type is limited in terms of actually good attacks...), and here's where Frenzy Plant kicks in. A 225 Base Power attack is not to be underestimated. Just 25 points short of Explosion. And seeing how Meganium's Grass Moves are just OK at best, it should be at least looked at. Hidden Power Grass is good, but you'd rather have Hidden Power Rock if Ancient Power is just too weak. Meganium isn't much suited for a Sunnybeamer, so Solarbeam is not a good option. Razor Leaf is about her best attack, but it's severely weak despite the enhanced Critical Hit ratio (This is no RBY... oh the irony. Hyper Beam was somewhat g0dly in RBY too. XD.). Heck, with her limited Offensives, I believe even a Swampert could take a Meganium's Razor Leaf. Giga Drain is also OK, but that PP... just sad.
Frenzy Plant balances out the lack of offensives in Meganium's regard. She can take down a fair amount of Pokémon she wouldn't be able to with the likes of Razor Leaf or Hidden Power Grass. It'd put a severe dent in Pokémon like Suicune and Milotic, or even finish them. Yep, I know there's the recharge, but look! Meganium is a natural Tank. She can take at least 2 hits before going down. Or even more. In this regard, she has a quite high chance of surving the recharge turn. Plus, it'd be rarely used. Only for those rare situations where they leave their Water Pokémon out or when they just trust their unSTABed Ice Beam too much. For the rest, Ancient Power has NO weak in this regard.
Even so, I think only Meganium can use her Elemental Blast well. The other Starters that get it have decent enough Offensives to use other Fire, Water or Grass Attack. Maybe on Feraligatr or Blastoise, but both get Hydro Pump, which is a MUCH better option in every regard. Plus, Surf isn't too shabby either. The Fire Starters have Flamethrower and excellent Special Attack. 'Nuff said. Venusaur, while still as limited as Meganium, has a very good Special Attack ratio, which assures a decent use of even Razor Leaf. It comes down to the very limitation of the Grass Type in regards of offensive Moves. Until they get a 95 Power, 100% Accurate attack (Like ALL the other Main Types. And Grass IS a Main Type WITHOUT such Move for 3 goddamned Generations...), Frenzy Plant isn't a bad thing. More of a VERY good alternative, at least in Meganium. Sunnybeamers are too risky unless they have Chlorophyll, which isn't Meganium's case. The other Grass Moves don't pack enough punch with her Special Attack...
Still, I just think this is about the only exception. Slaking CAN use Hyper Beam to some extent, though yet again, Return packs enough punch. It's still a viable choice, because the "Metagame" isn't limited to NetBattle... there are MANY Metagames, and they vary with the area. Yes, they might not be THE Metagame, or there could even be no Metagame at all (Areas where zero to no people play Pokémon.), but one should adapt to the environment's exigences. Us that play the games go though hard work, not drop-down menus. We don't have to be 1 point higher or lower Speed-wise, or care about making our Pokémon's HP divisible by 16, 4 or all that shiznat. We just work with what we get. Yep, there's those that aim to perfection in regards of IVs, which IS a downright waste of time in the cartridge. We're also not limited by unnecesary restrictions, and most do play with our favorites regardless if they're OU, UU, NU, NEEEEEEEEEU, I, UUUUU or whatever. We still abide by the Rules Nintendo enforces in one way or another, such as the Sleep Clause, and even the 00ber Clause. However, the rest doesn't has to be claused...
Why is that? Because, as you experts say, it's luck-based. Hax is a loosely-used term. In fact, Hax implies illegal actions, not luck-based ones. It's an already established term in the videogaming community... and it's downright cheating to win. Hax is a Tyranitar with Aeroblast, or a Charizard with Thunderbolt. THAT is Hax. Double Team, OHKOs, and luck-based Items AREN'T Hax. They're legal, as they can be used by everyone and even receive a bit of support here and there. This isn't cheating. It's just relying on luck-based moves. I don't encourage the use of luck-based strategies, but I acknowledge that they CAN be beaten, and should be admitted instead of claused. After all, if ANYONE feels lucky enough to trust sheer luck, then so be it. If you lose against someone that used "Hax" (And I use this term loosely too...), then your Team wasn't prepared for such situations. Yes, I know NO Team is made to beat everything, but you should adapt to the Metagame, as I said. If I see the use of Bright Powder, Quick Claw and the like rising, I fit a Pokémon that can use Thief or Knock Off so their Item is rendered useless. If there's an up rise in the use of OHKOs, I bring in a Sturdy Pokémon to stop them right in their tracks. I already counter Evasion with Aerial Ace and Magical Leaf, because those are actually nice attacks, and I'm not power-obsessed, as are most NBers...
Why instead of confronting the problem, you just ban it? You all, more than everyone else, should know that luck is something you can't rely on. You lot, more than us, know and test the Pokémon in the Metagame frequently, and know what counters what. Yet you still ban this "strategy" like tough, yet scared individuals. This kind of restriction is what stops me from going into NetBattle. I don't wanna go and confront countless Boahs, Skarmbliss, Espyjumps and all those "Standards". I wanna go and confront people that use their favorites and various strategies, instead of stale and well-known ones. That would so give me a WAY wider view on how my Team fares overall. Beating OU after OU doesn't shows jack. I only had a total of ONE enjoyable battle back in GSBot. I soon found out those Online Simulator programs were too narrow-minded and too focused into winning instead of having fun and testing their favorites against others. They already lacked the very soul of this concept, having only to choose your Pokémon, Stats, Moves, Item, and presto! You have your piece of data. But the "Metagame" added salt to the wound...
But well. I just think there should be a more open mind. I do agree that those Moves aren't very reliable, but they can be regarded as alternatives. I don't like them much either, but I'd like to try a Meganium with Frenzy Plant someday. It does balance out the Pokémon. There are endless possibilities in Pokémon, and we shouldn't regard anything as "useless" right away... for there's not only a single Metagame. There are many. And Pokémon should be used without restrictions, save the vital ones, because they DO balance this game (00ber and Sleep Clause.). I just notice that many people let this "competitive" stuff get to their heads too much... when there's MUCH more than Boah and all that jazz...