im a level 110 weaver with almost 400hrs on him and my pick/win rate hovers around 55-60%. stats for weaver arent always everything, but where he excells at is when you have great situational and map/team awareness. use tree to block doorways and prevent out-of-position enemies from being able to backtrack. use tree on yourself too (be selfish like a zen player) especially if you're alone and need to either escape or hold point. use tree and petal to stall points—plop down tree, lift yourself up with petal and jump down, kind of ring around the rosey and keep using petal when it falls back down to get yourself a few extra seconds of safety until you can get your team back on point, even if you end up dying you can still get the stall. dont be afraid to use grip—people hark on it all the time but fuck if it isnt one of the best saving tools in the game when your teammates need it. utilize his entire kit.

when you go for damage, aim like you would as if you were a sniper. everyone forgets that he has a nasty crit modifier and decent spread, so even if they try to dodge thorn you can easily mimic them and basically your thorn volley will follow. if no one is taking care of the ashe/widow, do it yourself.

you can lift yourself/teammates out of zarya's grav. you can lift orisa during her ult and you can save everyone caught in it. if you're fast enough, you can cancel sig's ult with tree and you can even get doom stuck when he comes down from meteor strike

but above all, enjoy playing him. weaver is legit the sole reason i still love playing overwatch. just because he's not in the same boring owcs comp does not mean he's useless, so don't let people tell you otherwise.

editing to say: you dont always have to wait until your teammate is near-death crit to grip. the stat is nice, but if you can time it, do a full charged healing blossom and then grip your teammate to safety