I'm absolutely with you on this one. Of course it all depends on what you want, and clearly there are people who value heated seats and a built-in satnav and all the rest of the toys, and who am I to say they're wrong. But most of that just doesn't interest me. (And - ssshhh - I think the spoilers are ugly.)
I had a Golf GTi before this car, and it had heated seats, but last winter I suddenly realised I'd forgotten I had them! While I was still working my normal winter routine was to get in the car, put heating to max and switch on the heated seats. I'd have gone about 10 miles before the car was warm enough to start turning things down. But having retired, then not driven much in 2020 because of covid, I actually forgot about them! That did influence my decision not to care about them in the MG4. But more important was the pre-heat facility. If I can heat the cabin up before I get into the car, that's more important to me.
I've never used a satnav, so I can go on doing without it. There are a number of little things where it's - oh that's only available in the Trophy! - but nothing I really care about. The SE, bar heated seats and electrically folding mirrors, has just about everything the Golf had. (Oh, the Golf had dual heating controls, which was nice, but the Trophy doesn't have these either.)
The one deliberate thing that annoys me on the SE is the lack of electrical folding wing mirrors, but in fact I can get the car in the garage fine with the mirrors unfolded, so it's hardly a deal-breaker.
Other annoyances are the lack of folders on the USB player, the inability to turn off that awful auto-locking thing, and the way the radio keeps coming on even if you just turned it off. I think these are software glitches, rather than deliberate punishment of SE owners for not spending more, and they might be fixed.
As regards the SR or LR battery, I'm very happy with the SR as it has enough range for my normal daily driving. I know I'll spend longer charging if I go on a long trip, but that wasn't worth an extra £2,500 to me. Also, the SR is easier to manage, just charge it up to 100% whenever you like, it doesn't have cobalt in it, and it's reputed to have an extremely long life.
For anyone relying on public charging using rapid chargers for their daily driving though, I think the LR has to be a no-brainer.