Why must we turn off Wifi to ensure consistent cellular connection? iPhone SE 2020

The Apple Store "Genius" told me to "always" turn off Wifi when I leave home in order to use cellular internet connection. This has never been the case before, the phone just used Cell data as needed.

I'm an Uber Driver, and after a period of time being online, I will see "trips paused, no internet connection" if I leave Wifi turned on and depend on cellular data for my internet connection. Then if I go to Settings/Wifi and turn off Wifi, I will usually regain connection, but not always. This is especially true after I've been in the Airport Uber driver waiting area for a little while; upon first arriving to the Airport, I have a good signal, but after a time I am no longer connected. The Uber app especially does not like being in the "background", like when I'm checking flight info or email or reading an ebook. When I switch back to Uber, I find I'm no longer connected and must turn off Wifi, cycle off/on cellular data, or even power cycle the phone to re-connect. Usually at this point none of my internet apps will connect.

The Apple Store diagnostics say the phone passes all the tests, and I've gotten a replacement SIM card from Cricket, my cellular provider, but the problem persists. This has been going on for a couple of months to one degree or another. The Cricket Rep blames it on Apple switching to e-SIMs, which I don't use.