No game is perfect. No matter what you see online about "Call of Duty" having absolutely no issues, such can simply not be true. Theres no such thing as perfection. Everything is bound to have some sort of issue, or sometimes even an explanation! You may be asking, "Why are legendarys so hard to catch?" Because they are legendary Pokémon! They are so obnoxiously overpowered that to rebalance the game they need to add such crazy low capture rates, and outrageously high CP values during the raid battles themselves. "Why did they revamp the gym system?" Well, sorry to all of you who would perch your dragonites atop the gyms and sit upon your thrones as you racked up pokecoins, but it simply wasnt fair. Pokémon Go has new players joining (and leaving,) every day. It wouldnt be fair for a full group of level 32 players to set CP 2500 Dragonites in 13 gyms, then leave as newer, younger players are powerless to take them down. This system allows a much wider audience to enjoy gym battles and free pokecoins. Most people, (the people who arent so angry they waste time trying to make the game look bad,) really, really like this new system!
So deal with the issues, and move on with your lives.
Its just a video game people!