They might, like DDG, promise not to track me and to respect my privacy, but as an ordinary user I have absolutely no way of verifying their claims.
I don't trust Vimeo any more than YouTube. I don't trust Authy any more than Google Authenticator. FastMail is great, but I don't want it to have my email any more than Gmail. I don't trust Firefox any more than Chromium.
Unfortunately the internet and computers in general were never designed to respect privacy and most corporations are happy to collect data on their users... and I'm pretty pessimistic on this changing much for the typical user... If anything it's only going to get worse as tracking technology becomes ever more sophisticated and omnipresent.
That's not to say we shouldn't deGoogle. But we should be under no illusion that that alone will somehow magically make our online lives private.