There’s no way around it … You were wrong in the first place 
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It depends on the individual Apps.
Banking Apps have proven to be especially tricky because of their security concerns, but there’s a bunch of them that will work, see [LIST] Banking Apps on /e/OS - #138 by mac - Lists - /e/OS community.
In general, thanks to the included microG (Open Source replacement mimicking Google services to some degree), many Google-dependent Apps (these are many, not only Apps by Google) will work just fine, but there’s no guarantee they will do so at any certain point in time.
If you really desperately need any particular Google-dependent App to work for you near 100% (or alternatively to have a chain of responsibility you could take it up with if it doesn’t) … then /e/OS is not for you.
/e/OS is not for you. Custom ROMs in general are not for you. Don’t risk stuff required for work not working correctly.
There’s a lot of goodwill and amazing expertise in the Custom ROM communities, but when push comes to shove, it’s mostly voluntary effort.
Fairphone OS, like most phone vendor stock Android OSes, is Google certified. You can take up App issues with Fairphone support. If they determine it’s a real issue in the OS code and Fairphone didn’t cause it themselves and can’t fix it on their side, they can take it up with Google to fix it more closely to the Android root.
Custom ROMs don’t have that kind of relationship with any official entity. If they can’t get an App issue fixed with their means (including perhaps reporting back an issue to Google, the basic Android all Android OSes are forked from is Open Source afterall), then so be it 
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It might be a major selling point for users who synced their stuff to Google before and need a replacement for this when switching to /e/OS.
For other users … not so much I guess, they will have other measures in place already, like you do. If not, they could perhaps be interested in it because it doesn’t sync to Google, but I’m not certain how major this would be then, might be different individually.
I don’t use their cloud account, so I can’t say much about it.
These are mostly bugs, and not general ones (not everybody suffers from them), hopefully to be resolved for the ones affected. Regarding geolocation sometimes there’s even only a misconfiguration which can be remedied quickly.
/e/OS is a compromise in favour of App compatibility and overall accessibility. The target group clearly are users who are not so tech-savvy, and /e/OS caters to them pretty successfully.
Other OS options might be more fitting depending on priorities.