Apparently. I mean, the guy explicitly used "forgetting which exhibitionism content he'd done" as an example of an inefficient system he'd like to see improved, which certainly strikes me as evidence that some people need a way to track it. Perhaps they last played the game four months ago, and can't remember which content they completed. I don't know, and I don't need to know to acknowledge what they're saying. Not all people consume game content in the same way; the fact you're even questioning this is a little strange to me.
You do. I did. Clearly, not everyone does, and I think assuming people all behave the same way is a bad idea.
Nobody said it was hard.
What the guy DID say, was that the current way to check if you've done all of a particular type of content (in this example, exhibitonism ) isn't very efficient. He is correct about that. He mentioned that the at-a-glance option available in the mod was a far more efficient option. From the images he showed of the mod, he was correct.
Some of the replies to his comment suggested that just going to each girl, taking them to their respective exhibitonism scene hubs, and checking that way was just as good a way to check as the method he was discussing. They are objectively wrong in that assertion; I used Lin as an example, but feel free to try it yourself and see how long it takes you to check them all. Then compare that to how long it'd take to check based on the images he included from Lain's mod.
No it doesn't, it tells you how many times you've earned exhibitonism points with them; not everyone does each scene once, in order. If a person has five points with Lin, that doesn't mean they've done all of her scenes once. They might have did her first one three times, and her second scene twice. If they can't remember and would like a way to quickly check, the way from Lain's mod is indisputably quicker than checking each girl one-by-one, and I'm not sure why people aren't engaging with what the guy was actually saying.
Again, nobody said it was complicated. I'm not sure why you're acting as if they did.
The guy said the game doesn't contain a way to check which content he has and has not been completed which is as efficent as the way Lain's mod contained. He is correct.
He pointed out that if an option is one you haven't unlocked yet, then Lain's mod also tells you what you need to do to unlock it (Kali friendship 11, for example), meaning you're not going to waste time trying to unlock it until you've acheived those requirements; he also said the the game does not explicitly state those requirements anywhere near as clearly. He is correct about that, as well.
Now, how many people need such a system? I've no idea. It could be just this one guy, but given the amount of people who ask after updates to Lain's mod, and how many people have said they find the mod very helpful, I'm willing to say it's not just him. I'm further willing to say it seems to be quite a few people. I'm unwilling to estimate a proportion of the player base; not enough information to come to such a conclusion.