Android has some viable non-root "application firewalls" or other apps that use Android's VPN functionality to filter traffic. These can prevent apps, including system apps, from accessing remote servers, e.g., DNS resolvers, ad/tracking servers, etc. There are also Android apps that can automate killing apps that try to run in the background
Not sure iOS has anything equivalent
The problem with "apps" isn't the surreptitious attempts to access remote servers for data collection, surveillance and tracking/ads. Websites do more or less the same thing. The problem is that the corporate mobile OS sucks, it's user-hostile and exceedingly difficult to try to control
The advantage of websites is they do not require using a computer running a corporate mobile OS
The corporate OS may also include terms requiring arbitration to resolve disuptes
At least in the case of Android, an advertising services company OS, those terms may be on a remote server (owned by the company), not on the computer owned by the "user".^1 As such, the user may block access to them along with all the other advertising-related garbage
Not sure iOS has anything equivalent
The problem with "apps" isn't the surreptitious attempts to access remote servers for data collection, surveillance and tracking/ads. Websites do more or less the same thing. The problem is that the corporate mobile OS sucks, it's user-hostile and exceedingly difficult to try to control
The advantage of websites is they do not require using a computer running a corporate mobile OS