This is frightening. I just started the process of moving all ~60 of my domains from Amazon Registrar + Google Cloud DNS to Cloudflare, and will definitely wait until somebody from Cloudflare chimes in here to clarify what's going on.
Don't put all your eggs in one basket, ie. don't just use one provider. Also for your core domains, do not let the registrar and dns provider be the same entity. Also, don't decide on not migrating just because of one bad experience. None of them are perfect, though vigilance is wise. (I know am probably preaching to the choir :) )
Consolidating domain registration, DNS hosting, and site hosting under the same account is a terrible idea and a big risk IMO. Always ask yourself “what if this account gets banned?” All of the big tech companies have automated systems that could turn you into an outlier with no support.