The "can't" comes from the fact that VLC is not going to rewrite their forum software or software forge.

Software written in PHP is in most cases frankly still abysmally slow and inefficient. Wordpress runs like 70% of the web and you can really feel it from the 1500ms+ TFFB most sites have. PhpBB is not much better. Pathetic throughput at best and it has not gotten better in decades now.

I don't know how GitLab became so disgustingly slow. But yeah, I'm not surprised bots can easily bring it to its knees.