My boss used to have an apt sticker on his ThinkPad that said 'My other computer is a data center'. In my case that's also true; I just use local I/O for KVM but the heft is in whatever I'm SSH'd into.

I daily a T480 at home and an X280 on the road. Swapped the batteries for fresh ones last week, they do around 6 hours on a charge for my use case and they run Linux so personally I don't see any reason to upgrade any time soon.

I don't remember the T480 I had was any slow, except of course when running games. So I do agree that the machine is still capable for most use cases today.

But I also saw people (usually X series users) complaining on YouTube saying something like their "mobile" CPU is trash etc. My thinking is, if the slowdown is actually insignificant for real-life use cases, then I rather have longer battery life than better performance.