I have found that keeping up with the modem capabilities of the average person's phone has been historically important for getting good signal strength and service in general.
I don't know if this is a resolved problem with 5G LTE and/or how backwards compatible 5G is with 4G (can they share spectrum? I honestly don't know, and perhaps it all depends on the particular carrier and how they allocate their deployments), but in the past you could notice that your 3G service would be a lot worse in its latter years of deployment than the 4G service simply because most customers had 4G and the carrier was allocating way more spectrum and bandwidth to 4G LTE service.
So you think about the median person replacing their phone every 3 years and you can figure that basically everyone in the US now has a phone with 5G capability, that's the service that cellular carriers are going to prioritize. That's also the level of service I am paying the carrier every month for.
And yes, 5G does get me a lot of great stuff like that. I actually tether my phone to my laptop or gaming handheld and play streamed games on it. I also work with large files so I can upload/download those large files to a server while I'm on a commuter train or in the passenger seat of a car. I can join video conference calls and things like that without issue.
I also personally switched from Android to iPhone specifically because so many carriers test iPhones so extensively (and there aren't an overwhelming amount of SKUs to test). The iPhone seems to have fewer carrier-related glitches in my experience. For example, I have a family member who switched from iPhone to Android and subsequently experienced call drops to their international calls consistently on their Android device (even after replacing the SIM card and other troubleshooting), but they resolved it entirely by switching back to an iPhone. Their carrier just didn't test out that particular Android phone that well, I guess. But the underlying reasons were irrelevant, they just need a phone that works for the purpose it's supposed to perform.
Considering that cellular service is the most expensive part of phone ownership, it seems to me that having a shitty device that can barely utilize the network's functionality is a way bigger problem than the device not being open source or not being Linux based or whatever line in the sane that Librem markets their very expensive phone under.
And of course I haven't even gotten into convenience features that depend on the proprietary app stores or carrier-integrated features like banking, transit cards/boarding passes/wallet functionality, CarPlay/Android Auto, visual voicemail, having a camera on hand that competes well with standalone point and shoot cameras, but I guess a Linux/Open Source die hard doesn't mind going back to the previous decade for those things. Still, those features are pretty damn enticing.
I can understand if you don't want those things but we have to remember that Librem is charging iPhone money for a device that does less things and has worse specs than a basic $100-300 Android phone.