Tailscale’s official clients are FOSS on free platforms and there is an officially endorsed FOSS back-end (headscale) if you wanted to self-host a fully FOSS environment.
Of course, hosting headscale requires a public server which you may not want or have the ability to host and in those cases, using their proprietary back-end as a service is absolutely fine in my books.
As a company, Tailscale has generally struck me as quite the opposite of “garbage”.