You still get much better privacy with GrapheneOS even if you install Google apps since they are sandboxed; they don't have access to unique device identifiers and you can control what Google can access by adjusting its permissions, as opposed to having full reign to do whatever it wants. Also you don't have to use all the Google apps, plenty of open source and/or privacy respecting alternatives out there. Pixel Camera only needs Google Photos for the photo previewer, everything else works without it or you can install gcam services provider to use any gallery you want

The outlook app works for me on GrapheneOS, is there something about it that doesn't work for you?

Many banking apps do work on GrapheneOS, the list had already been linked to by others