Whatever system is used, there will be complaints about something. Nothing is perfect. So the issue isn't that there is some feature lacking or not working as expected, but whether having that be better (possibly still not perfect) justifies breaking something else or making a larger annoyance.
Would drag'n'drop images, for instance, justify endless scrolling? I guess, if you can't stomach temporarily saving an image to disk (RAM disk here, but I realise that's too expensive for many now

) and post an image in every comment then it probably would. Or once in a blue moon you want to paste some random image off t'web and that brings the lack of pasting to the fore of your consciousness. But the downside - endless scroll in this case - doesn't seem bad because you don't experience it.
SMF sucks, and it is a pain to use this forum in 2026, compared to others
The thing SMF lacks, which not many others implement either, is proper threading. Not having to quote every damn previous post, so the reader knows wtf you're commenting to, is bloody fantastic and natural[
1]. But that's old fashioned and the 2026 thing isn't pasting images but posting video clips. Doing stuff because that's the want du jour isn't always better.
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[1] With proper threading the major beef isn't that posters don't quote previous comments, but that they
do quote previous comments. Just as many whining about excessive quotes on those systems as those whining about lack of quotes on here.