Is serverless just for simple sites?

I’ve done a few simple Nuxt static websites (portfolio\client stuff) on Netlify

But now I want to build a real app\saas and while I LOVE Netlify, am I in for a world of hurt without a server? Like I’ll need authentication, protected pages, a database (somewhere), and I guess netlify functions. Seems like a whole bunch of extra monthly costs, but I just love the scalability…

What concerns me most is the death by a thousand cuts with functions\saas database. Like if one tried to build Asana on the Jamstack (not that’s what the plan is, just an example), would that be an extraordinarily bad idea?

Has anyone made anything of scale that worked well, were you surprised by the costs (either high or low)?