I have actually hit the same hurdles (also predominantly Fi). I found two carriers and have been thinking about switching.
Cape (https://www.cape.co/) seems to be a neat option. It's an MVNO (just like Fi) and is very privacy oriented. It's definitely not as affordable as Fi, but it's not terrible IMO. You're paying a premium for the privacy aspect after all. It's $100/mo for unlimited talk, text, and data.
Phreeli (https://www.phreeli.com/): another privacy oriented MVNO (I think it's an MVNO). Has more affordable plans with prepaid options for data (more similar to Fi in that respect). Their flex plan is unlimited talk and text, with 2GB of data for $25/mo. Each additional 5GB is $20 (with rollover).
I don't have a recommendation for the phone app as I also have been using it. But I plan on just cold turkeying after I switch carriers.