Exactly. The internet connection shuts off at the most inopportune moments like when you are navigating or stuck in a city, or when you need the internet most to look up or reply to a work email. Almost always happens mostly on the cellular network. I almost switched out of the T-Mobile to Verizon but then I saw my son's and wife's android phones working flawlessly and running even full on youtube videos while I was struggling to even open an email or a webpage on the very expensive 'iPhone 12 Pro Max'. We need a fix pronto @"APPLE". For Lord's sake this is your flagship and you are having issues on one of the most basic functionalities of this phone.
Also, as some others have said, it has nothing to do with Doordash or some of the apps, might randomly fix issues, but I am guessing the issue inherent somewhere in the software or hardware of this particular model.