On reddit everybody says they hate the player battles because the game is glitchy (true) and it's a "stupid paper rock scissors"... but that last part makes it fun. I think they're just mad that there's finally a component of the game they can't win every single time. They take it too seriously.
fairy beats fighting. fighting beats steel. steel beats fairy.
obviously not everybody hates it, because any time you want to battle, you can enter and get instantly matched up with an opponent. it is constant.
I started out picking the pokemon team that everybody else put out. if everyone kept beating me with skarmory (steel/flying) or azumarill (water/fairy) I'd think, "well then I need to throw out skarmory and azumarill!" and then it's a contest of whose skarmory is SLIGHTLY BETTER and gets to sky attack first, or we battle our two azumarills in the most boring match ever trying to "not effective" each other to death. But when the master leagues came around, I adopted a different strategy of trying to watch the trends, which do change from day to day, and try to pick the pokemon that would beat whatever everybody else is throwing down.
so we're in great league week right now, everything under 1500 cp, and my team is:
Wigglytuff with charm, ice beam, play rough - for taking giant chunks out of obstagoons, altaria, the occasional umbreon. faced with a grass pokemon I can sometimes ice beam it but it takes a long time.
Fire Castform with ember and weather ball - it's fire so anything grass goes down quickly and it can take out all those Skarmory
Serperior with vine whip and leaf tornado - grass to take out the azumarill, leaf tornado lowers opponent's attack.
My all-time stats show me winning about half the time. I feel like recently I'm averaging more 3/5, but there are bad days. I have a tough decision to make if someone throws an Ivysaur first... they have poison moves that will take out my wigglytuff. but if I switch to castform to kill it with fire, they can switch something water to kill it and with the switching time limit I'm stuck. that is the game, and you deal.
I never run from a match. I finish every one even if I'm losing. Learn what other attacks affect my team. Other people run away and let me win and that's great, but I am a pokemon trainer of honor.