I have very mixed feelings about Cloudflare. It can be great and it can also be much less so depending on the application.
One of the problems is that it lulls people into believing that they don't need to look at or worry about why their site is slow in the first place, because sticking it behind CF and switching on everything you can will just make it all ok. It's covering up a problem rather than fixing it.
Used as just a DNS provider though, with all of the little orange clouds turned off, it is absolutely great. Very fast and reliable anycast DNS for free, there is nothing else that competes with that.
As an aside, real user speed experience is more important than all of the metric sites, and you can't really rely too heavily on what any one of the tells you, because they will all tell you something different, there are so many variables in their testing.
As an example, I just tried the same page on the same site in PageSpeed Insights and then in Bytecheck.
Pagespeed gives it a score of 93 on mobile and 100 on desktop - total loading time is 0.6s on desktop
Bytecheck gives it a score of 2 out of 5 stars - with a time to first byte of 0.9s and total loading time of 1.1s
