Smogon

I find smogon to be a great community who make competitive battling far more interesting. I love VGC formats, but I think in terms of diversity of teams it has nothing on the smogon tiers. You can take practically any Pokémon, build a team around it and use it competitively in their respective tiers. In VGC, unless it has a very specific niche, such as Lapras in the VGC16 format, you won't see it used. They don't force their ruleset on anybody (regardless of what certain youtubers might have you believe) and recognise that they are an unofficial format. It's just a more fun format overall, with much less RNG dependent games overall (looking at VGC16 for example, games often rely on attacks hitting, speed ties and making assumptions of movesets from team composition).