But like people who started at the beginning, you can level up to the point where you can take on gyms. You're a little behind, but work at it and you'll get there.
This.
Also, one of the important things about the level-to-gym discrepancy is that you should remember you
can't ever challenge gyms right off the bat. Think of it like this: in the main games, do you just walk into a gym and say, "Hey, what up, Brock? Here's my level five Charmander"? No, of course not. You catch bunches of Pokémon and train them until you
don't get floored by the gym leader. Same deal with GO, except they just use a different system. So whereas you can catch whatever in the main games and level up that whatever you just caught until it can beat Brock, in GO, you go around, catch Pokémon until you find one that's suitable for your neighborhood gym leader, either because it's already strong enough to beat them or because it's at a reasonable amount of CP where you can just forcefeed them candies until they're strong enough.
And before anyone says, "Okay, so they should just bring battling into GO," keep in mind that the medium's different. It
already takes super long to catch Pokémon. Imagine having to
battle them. Battling takes a lot of time in the main games—at least a minute or two. That's great if you're standing in one place, but because GO is all about movement, that one minute is the difference between you finding a Pokémon you need and you bypassing it completely, especially if you're playing by car. While, yeah, we're already joking about people hanging out around Pokéstops, ultimately, GO's supposed to rely on quickness so you can move from one interaction (be it spinning a stop, catching a Pokémon, or checking into a gym) to the next as quickly as possible.
Tbqh, though,
that might be where GO's weak spot is. I mean, don't get me wrong. I get why gyms and teams are a thing, and I get why the difficulty in catching Pokémon scales with your trainer level. And also don't get me wrong, I'm a little hesitant about comparing the game to Ingress
yet again. But the thing about Ingress is that a lot of its gameplay relies on team synchronization. Absolutely, you're spending a lot of time hanging around portals to take them down too (Ingress is basically the gym part of Pokémon GO, only a lot simpler because you're just selecting a weapon and mashing the fire key—which is weirdly a lot more satisfying than it sounds), and absolutely, you can't really do anything when you're just starting out. (Attempting to hold a portal with level 1 equipment or attempting to take one down with level 1 weapons will get you very frustrated, very quickly.) But the whole point is basically you connect with your team, and they help you to level up, get what you need, and set up portals.
The bizarre thing about GO is that the teams are there, but the team
synchronization isn't. There aren't really communities dedicated to Valor, Mystic, or Instinct the way there are for Ingress's Enlightened and Resistance. You can't really communicate in-game with your teammates, and I have yet to hear about people setting up Slack channels or other mobile channels to connect on a private level with each other. Likewise, a lot of the old hats aren't really reaching out to help the newbies like they do in Ingress. So I can definitely understand that tackling gyms can get frustrating because by and large, you're kinda on your own—there's no real sense of people strategizing to set gyms up unless you're doing it with your friends.
Now, don't get me wrong on all of this either. I'm still having a lot of fun because I find it weirdly addictive to catch Pokémon. That and while I adore Ingress and its team dynamics, you get instant gratification in GO for playing it every day. I'm just saying that if you play GO for the gyms, it's understandable that it might be a lackluster experience. It almost seems like Niantic hoped the game would be more like Ingress in that respect (and they did indeed give us all the baseline tools to
make GO be like Ingress Lite in that respect), but the problem is folks just aren't forming the communities to do it. Whiiiiich I know sounds like I'm blaming the fandom, but I swear, I'm not. Niantic attempted to make a game that appealed to the center of the Venn diagram between their fans and Nintendo's fans (which is a perfectly reasonable aspiration), the audience they wound up getting were folks who've never played Ingress, and the end result is that Niantic and the fandom had different expectations for what the game was meant to be.
Or tl;dr, the point is that it's an AR game, so a lot of the problems you might encounter if you're here for just the gyms might stem from the fact that lots of folks either encourage you to play this (or think you're supposed to play this) as a normal Pokémon game. ¯\_(ツ)_/¯