Mildly Infuriating

I'm increasingly trying to use my (GNU/Linux) laptop where I can, and just tether the phone to it when I need mobile data connectivity.

It's not a complete drop-in solution. You can't just use a laptop with one hand while waiting in a line (well, there used to be palmtops, but those seem to be a mostly-dead class of PCs today). It consumes more power. Desktop OS software doesn't really natively have a concept of "being on WiFi versus being on mobile data", which is nice to have in phone software.

But where you can sit down and use one...man, it eliminates a ton of my irritations with phones. The locked-down stuff in most phone OSes. Those fiddly, limited onscreen keyboards. The tradeoffs that the systems make to try to minimize power use and simplify memory management from an end user standpoint (because a lot of users don't get the concept of closing programs) like the one you mention go away. Hardware is more capable and expandable, and the manufacturers have way more physical space to work with, so you don't have manufacturers throwing out things like physical headphones jacks to try to get a bit more space. The limited cooling on phones goes away. Better in terms of repairability

I just replaced a laptop battery. If my phone's battery died, I'd throw out the phone. Using multiple programs at once, as you were doing, is much better; phone OSes just aren't really optimal for that.

I'm honestly impressed with what smartphone vendors have done within the constraints of what they have to work with, especially in how much better touchscreens have gotten over the decades

they used to be far, far worse. But they still just face a ton of limitations imposed by the form factor.