I challenge others that think the game is so easy to do the same. Think about your first game and tell me that there wasn't at least some part that you struggled with.
There was a trainer at the end of rock tunnel with a Bellsprout that used wrap. There were no survivors. (For those who don't know/don't remember, Gen1 trap mechanics were crazy).
I think one thing to remember is that Gamefreak's priorities are roughly:
1. Sell Games
2. Provide the joy of collecting and exploring
3. Promote Socialization
4. Finally, battling.
(5. Raise awareness for accidents caused by riding bikes indoors. WHEN WILL THEY FIND A CURE?!)
Another thing we forget with Smogon and easy online simulators nowadays is that there wasn't an easy competitive format in-game for PVP matches on the likes of League of Legends or what have you. Up until Gen4 we were stuck with link cables and physical interaction, and I'd argue that even after the advent of online multiplayer it never got user friendly enough for a major audience until the Battle Spot for current Gen6. Before that battling your friends wasn't easy or as fun so Gamefreak didn't focus on it. Yeah they had some tournaments, but back in the day those were still a niche. So we created the sim's around Gen3ish to fill that gap, but Gamefreak has no part in simulators.
So if a developer after at least 3 generations of semi-neglect to the competitive crowd went back to try to perfectly balance 700+ characters (heck, even just 350ish fully evolved lines)? Are you nuts? Balance is hard to achieve just with 8 characters, much less 700+. And that's not getting into alternate formats (4v4 double, triple, rotation, 3v3 single, 6v6 single, 6v6 double, inverse, air, battle facilities...) It's a wonder that we have what little balance there is.
And you know what? Gamefreak really has been trying. Honest. The streamlined connectivity a ton on the 3ds (opinion varies on if it's on par yet or not...) and eased up on the more complex stat mechanics (EV's, breeding, IV's, hidden abilities...) to make competitive matches more accessible to more people. And as for taking NU pokemon and making them OU, what do you think the Mega's are? (well, half of them, the other half is popularity factor). And let's not forget the little stat adjustments a few pokemon got, the addition of fairy type, hidden ablities and move tutors, the weather nerf, gamefreak is always taking steps for balance.
Yeah, they aren't perfect. I personally feel that the gap between competitive and in-game is too large and never teaches players basic competitive concepts like match-ups, switching, creating/exploiting free turns, or even using substitute correctly. Almost all because the AI never switches out. But balancing games is very hard, and mostly proven through experimentation and trial rather than any magic formula. If you want to experience this yourself, take part in one of the Create-A-Pokemon projects, projects meant to introduce just ONE balanced but unique concept into the metagame. Even with a bunch of people working to just create one pokemon, there successful track record is pretty slim (we've got what, Voodoom actually did what they wanted it to? And even then not HOW they wanted it to do that?)
So yeah, Gamefreak. They ain't perfect, but they try.
Final thought: a definition. These are usage tiers, not "these are the bestest evr u guyz." So even taking a Ledian and giving it the stats to fight there just means another OU get's demoted. There can be only
one 50ish! Maybe try playing a little NU or RU a bit. They're still as fun as the other tiers.