A lot of negative sentiment about Mapbox in this thread. I have been prototyping a (native) app powered by Mapbox -- would it be a bad idea to hitch oneself to their ecosystem?
Don't hitch yourself irrevocably to their SaaS. Make sure that, if your app becomes successful, you can swap out for Maplibre (the open-source fork of Mapbox GL) and an alternative provider such as Thunderforest, Geofabrik, Stadia or Maptiler. Mapbox have a lot going for them, but your app's success shouldn't be dependent on one company's tariff.
I'd suggest reading their terms of service and licensing model. They changed it on their 2.0 version and it stopped being right for a lot of use cases, either for financial, privacy or legal reasons. Make sure it fits for yourself also.