because sqlite is super simple to use and most things won't ever need to scale beyond one server.
Yep. But don't tell anyone. This is a secret weapon/super power most juniors (and many mid/seniors) have been conditioned by the GOOG/FB/AMZN/MSFT approved project literature to believe is simply untrue. The number of experienced, highly skilled founder devs I know that reach for shiny tech stacks that solve issues they don't have but can "scale" is a 100:1. That choice comes with staggering costs.
I suppose single node+db works fine for hobby SAAS and expert programmers who can squeeze every bit of performance from the machine. But for the average in-efficient programmer or teams, standard PostGres as DB and HA services fronted by a load-balancer work better.
Your project is far more likely to die within a couple of years from having too few users than from having too many. If you find you're having scaling issues then that's a good time to solve them - your project is popular enough to justify the investment.
You'll likely be recoding your project quite a lot in the early phase of the development anyway as you learn more about the problem and (most importantly) more about what your users want/need. Anything that can reduce the cost of this early iteration will pay dividends later because it makes it more likely that you'll need to scale - and by the time you do need to scale you'll be scaling something that you understand and other people want.