Layout shifts aren't a good look and should be below 10%. And while it might actually attract visitors in some contexts, shifts on a website might lead to page abandonment. But there's more to it.
"Critical CSS is a must-have for a good pagespeed and core web vitals score". I saw this statement passing by recently, and although using critical CSS myself, such claim comes with nuance.
Wondering why Lighthouse is recommending you to fix this, although you don't see any layout shifts yourself, and why is it warning you only now and not before?