What projects does the opensource world lack

Only Android Open Source Project, not the different phone UIs, vendor blobs, firmware, camera apps, etc... It is really the basics that are open source.

But also the source of android is 100% controlled by google unless it is an alternative forked project like lineageOS (at least I think so)

android yes, but the entire google play ecosystem is not, and some things are very hard to do without being inside that ecosystem.

I'm using my fairphone without any google account (so no play store), and it works, but there are some obstacles. Luckily my bank still offers a good website and even uses some international standard for 2 factor auth, so i can do my ebanking without the app - which, like most companies, is only offered in the play store.

for public transport, i downloaded the app from apkpure (in hindsight, the aurora store would likely be the better option) and it works fine for buying tickets. this is just my lazyness, i could buy tickets on the website (but it sucks) or at ticket machines, but the app is super convenient.

for various other services i just refuse to install apps. parking payments, my insurance company, work (luckily i have a bunch of freedom at work, using linux on my work laptop too)... is all stuff that would be convenient but it's all just available in play store. it looks like aurora is a good option, but 1. i don't know how long until google kills it and 2. i want to completely stop being dependent on adtech anyway.

That's not untrue but phones are complex, requiring lots of components and drivers to work together, so it's hard to get a fully free phone.