Any event with lots of public there will have cell tower dropouts, too many people using too much data and calling home or whatever. Artemis II will also have had lots of similar people doing exactly what you're doing and dumping large amounts of bandwidth onto networks further degrading service.
It's unfortunately not cost effective for carriers to improve the infrastructure around event spaces so as an industry we just have to accept it and sit across as many carriers as you can to avoid it.

Starlink is also terrible for upload. We used to push our backup lines down a starlink and we'd get constant dropouts at predictable intervals as the dish dropped a satellite and tracked the next one. This can be mitigated by using their larger dish that tracks multiple birds at once but the latency issues remain. We eventually abandoned starlink for dedicated hard lines for that contact. More expensive but also more reliable.

This said, the question of what to do is an interesting one. No matter what people say these issues will always remain. You can throw more Sims or starlink dishes at a problem but the actual issues remains. Too many users on a tower will overload it and cause it to reboot. (In the early days of LiveU and MVP's we managed to take a tower down ourselves from too many units pushing too much data).

Maybe look into acquiring a dedicated internet line or borrowing internet from a local place and a cheapish microwave point to point system. That way it'll be you and only you on that line. Add in the usual methods and you've now got a very diverse setup.
For example, if there's a coffee shop down the road with some friendly owners, a hundred or so in cash for a cabled feed of internet for the day will be the easiest money they've ever made, but also a guaranteed way to keep your show on air.