Yeah, specs future-proofing is completely worth it unless you do what I do:
I buy devices and never update them, so regardless of specs they all run flawlessly (well... Unless they’re forced out by Apple, that is). Don‘t get me wrong, however: my 9.7-inch iPad Pro is almost perfect performance-wise. Slight, negligible keyboard lag does not change my assessment. Performance has been criticized ever since iPadOS 13. So far, so good.
My 6s on iOS 10 is as fast as my iPad Air 5 in terms of overall, non-demanding usage (i.e., I am not running the latest games on both, not least because iOS 10 probably will not support them), and an A9 is totally inferior to the M1 on the Air 5, of course. But for what I use them? They both run perfectly.