Stack Auth is trying to solve exactly this — open-source, developer-friendly, and reasonably priced managed auth. That way, you don't have to worry about OAuth

Stack Auth is trying to solve exactly this — open-source, developer-friendly, and reasonably priced managed auth. That way, you don't have to worry about OAuth but still aren't locked into a specific vendor. The downside is that we only support Next.js for now (unless you're fine with using the REST API), but we're gonna change that soon.