If it was this easy, we'd have enabled this by default. Unfortunately by far not all UI freezes in IntelliJ IDEA are caused by GC, and ZGC is not a wholesale performance improvement even for those scenarios which do depend on GC.
A large issue is afaik the lack of memory reclamation and the over provisioning required to even really work at all.
This is absolute silly hogwash with nothing to back it up.
If you think the product hasn't gotten better, completely fair to share that. To blatantly claim you know the inner motivations of its workforce and they don't care about the product is not productive.