Congratulations. You are a technology literate 20-something year old and can easily find stuff like fan sites that explain these things. Similarly, children today are ignorant because they aren't on fan based sites. They aren't on computers unspervised often and do other things when they are on them.
You're ignoring how the demographics of internet users have changed over the years, by assuming that kids of X age today are exposed to the same level of internet content as kids of the same age back in the 90s. They're not.
And even so, the knowledge that advance mechanics exist shouldn't be a mind blowing fact to anyone (they pretty much exist in any number of games), nor does it change anything in how one plays. There is never a point in the game where you are forced to chain breed for an egg move or catch a Pokemon with a certain nature with Synchronize or anything advanced like that. Just like 10+ years ago. Pokemon has largely stayed the same in how it treats advanced mechanics. They're there, and it is up to you the player if you want to use them or not.
It isn't mind blowing per se, but it does irk players when they know they have the means to maximise the potential of their favorite Pokemon at the expense of time and perhaps, overall enjoyment of the game. Besides, which other game you speak of falls into the same category as Pokemon, which is a hybrid of RPG and pet raising game? Even if I were to go through the likes of Final Fantasy series with an in-depth guide to max out my character and basically do everything 100%, I do so with the mindset that that's the endpoint. For Pokemon it's a never ending process if you're into these mechanics, whenever you choose to train a new Pokemon.
The original post is based on the premise that there are no advanced mechanics in the old games. That is false.
Congrats on winning an argument on the internet over technical grounds then.
As to your point: Regardless of how the exact stats are calculated between Gen I and II, why does that matter? Does the change in a mathmatic formula suddenly make it THAT much of a difference? Or is it still something that competitive players will seek out and everyone else can safely ignore?
Uh, I'm think the maximum difference is 15 points per stats for a zero IV and max IV Pokemon in Gen I, assuming both Pokemon were trained without any specific means to level 100. Today we're looking at a difference of 31 IV, 64 points from manipulating EV spread to the desired stats and up to a 20% difference in stats with nature. Of course it makes a lot of difference. Just pick any Pokemon on Bulbapedia and look at its min/max for any stats.
Even for the casual players, they would find themselves in a position where their Pokemon isn't "as strong as what everyone else says", simply because they grind too much at the wrong place with the wrong Pokemon.
If anything, modern mechanics make it much easier for the casual player to understand the advanced mechanics and join in the advanced play if they want to. Rather than the games getting more grindy over time, it is now easier than ever to breed a decent Pokemon for a competition.
Pretty sure the 'mechanics' we're talking about has become more complex rather than simplified. What's simplified is the means to modify them: the ease of passing natures, IVs, training EVs etc. In fact I would think that Game Freak could have decided to shift Daycare to post-E4 in B2W2 so that players focus less on the breeding and more on the playing, at least during the main game.
Since the OP's title was whether the mechanics have made competitive less fun, I'll just say that personally I have no time for those various manipulation in-game, especially when competitive play usually requires you to optimize your team with time and changes to the metagame rules, which is why I just use a battle simulator whenever I'm up for a bit of competitive fun. All it matters to the program is the min/max of each stats, just distribute the points and it's good to go.