I can't wait for a new generation of children to be driven COMPLETELY MAD by the fact that if you don't do this completely insane thing 10 minutes into mario RPG in the middle of, functionally, a cutscene, you have permanently missed your chance to get this chest and frog coin
annoyingly, we had a pretty good guess what we had to do as kids, but we failed to do it on the first try and didn't want to reload from save
then in endgame when we got the coin detector or whatever it was, we knew damn well what the issue was but didn't want to believe it and kept trying to find another way
wound up replaying from the start. anyway yeah
but what we really need to explain is this was fun, at the time. at least, to us. if other kids disliked it that's fair enough; we were unusual in many ways and this may have been one of them
it wasn't a world where there were a thousand games a year, nor could we instantly access complete information on all their secrets. games were meant to be played and replayed over a couple months.
missable secrets were also entirely normal and harmless in the older, memorization-centric games, because you were playing from the start over and over, using knowledge to accelerate your future playthroughs. in a sense you were learning to read the game's design language to guess where secrets might be, the better to remember them next time.
the 16-bit era, which mario RPG hails from, was after memorization was no longer really a thing... but proper usability principles were still only gradually being invented, and lots of players still had the design-reading skills, so this was a hold-over. it definitely would have been better to leave this secret out or make it non-missable, but with the historical perspective it's easy to see how the designers thought it would be okay.
(today those design-reading skills are more of a detriment to enjoyment than an asset, because when you can see the design intent right away, everything feels so paper-thin and lacking in mimesis... oh well. they're an asset in other areas of life.)
