Clearly your best isn't sufficient for them
No, but actually: even if you're playing in the srs bns tiers of Clan Battles, you can always improve. I need to work on my Moskva routing, for example. My positioning's a bit greedy, and that cost two close games against hurricane tier teams last night. My aim's fineish, but I can do a better job of hitting Italian BBs. My micro-level movement also needs a bit of work. Stuff like this –
if you don't know where you can improve, that's the first problem. After every loss, there's always a brief fault-free discussion of what could've gone better for the team. It's calm, and the focus is on what could've improved strategically. This is how you improve.
If you want to *stop* getting stat-shamed, you have two solutions:
1. Git gud (see above)
2. Turn off chat
The game's community has its toxic bits. The question is if you ignore the toxicity (and shrug it off) or if you take the hard route of "getting better".