Someone brought up HG/SS again? I feel that I need to say something.
Why can't I just keep quiet for once?
Of course, I am only using 4 Pokémon, but even if I was using a full team of 6, I think I would still be at least around level 37. I did no grinding and tried to avoid burning through trainer battles to level up new Pokémon I caught (which I usually do and I think it's valid strategy in any Pokémon game).
I'm going to assume most people who have played HGSS and complain about it haven't played through it to the extremes I have and thus, don't employ any of the strategies I use. For a long time, it was the only Pokémon game I could play and I played it constantly. So as a result, I've probably cracked the code and am able to always get to the Elite 4 and have levels on-par with them (happened in my last playthrough 2 years ago as well).
I have only played through HG/SS three times in total, the last time was 8 years ago in which I sort of did a "speedrun" through the story part of the game. But it was still very slow as I am terrible at going through games quickly even when I try. On that playthrough, I just used my starter and two others I had traded over from another game, which meant they got boosted Exp. From what I can remember, I did not have to grind at any point during that playthrough of the game, my "team" of three was at level 50 once I got to the E4 (I explored every area in the game and battled every possible trainer). Oddly, it made the level curve in HG/SS pretty much perfect. In any other game, I would probably have become overleveled instead.
For my regular playthroughs of HG/SS in 2010, I used full teams of 6 Pokémon. I had to grind quite a lot during the games, but maybe it wasn't that much more than in any other game prior to Gen 6? Or before Gen 5, for that matter? I don't really remember, it was so long ago. But at the same time, I am a person who doesn't really have much of a problem with grinding as long as there are good spots to grind... which HG/SS actually lacks. Yet I still trained 12 Pokémon to leve 50 against wild Pokémon at ranges of level 30-35. Would I have the patience for something like that today? Probably not.
Also, I haven't played HG/SS to any extremes at all. In fact, out of the games from Gen 4-8 that I have played, they are the ones I have played the least, along with Sword. I don't think I have even reached 200 hours on any of my main HG/SS files. It was also several years ago at this point and my memory is getting unclear at points, so I think you make a good point here.
Of course, the level spike from Mahogany to Clair isn't near as egregious as the level spike from Blue to the Elite 4 rematch / Red. But most people who do complain about the level curve (at least in my experience) only complain about the level curve around Clair and the first Elite 4 battle. However, I can't in good faith actually measure how bad the level curve before Red is, becaue the last playthrough I did, I burned through all of the Kanto trainers training an Aerodactyl and Raichu and my team gained almost no levels as a result.
I think the level curve in the games is pretty awful from Whitney and beyond, though that's just me. But if I were to pick one area where the level curve is at its absoulute worst, it is the post-game. Wild Pokémon generally ranging from level 5-25, regular trainers at level 40-50, Gym Leaders at level 50-60, E4 Rematches at around level 70, Red at level 80+. That's just bad game design IMO. When I played through teh Kanto part of HG/SS, I just nuked pretty much everything with my teams but I could never grind against wild Pokémon since they were too weak, and as a result, my teams barely grew by 10 levels throughout all of Kanto.
In fact, I usually have more probem with the extreme level curve around the Elite 4 in DPPt. Even when employing the same strategies (only using 4 mons, no grinding etc.) I still end up a good 10 levels lower than Aaron. I think the reason that DPPt never get called out for their level curve is that they have more steady level jumps up to that point, whereas the levels in Johto remain at a stagnant ~20 until Mahogany.
Personally, I have less of a problem with the level curve in D/P/P because of two reasons. The first one is that the Sinnoh games give much better training spots thanks to the VS. Seeker (which is amazing compared to the awful phone system in HG/SS). The Sinnoh games also have wild Pokémon at higher levels, they are at level 40-46 in Victory Road compared to level 32-36 in HG/SS. The second reason is that Platinum actually did some attempts to make the level curve at the end of the game less harsh. In D/P, Volkner's Luxray is at level 49, compared to Cynthia's Garchomp which is at level 66! A difference of 17 levels. But in Platinum, Volkner's Electivire is at level 50 and Cynthia's Garchomp at level 62, which is only a difference of 12 levels. In comparison, HG/SS did little to nothing to improve upon the difference from G/S/C. I'd even say they made things worse in the post-game by making trainer levels higher, but keeping wild Pokémon levels low. This is very notable since Red which got upgraded a fair bit and the E4 got stronger in rematches, but the wild Pokémon are still as low as in the originals. Finding wild non-legendary Pokémon at level 50 or above is pretty much impossible in HG/SS, which is pretty much unacceptable. And as you say, D/P/P also have more balanced level jumps before the E4.
The low levels are also a pretty big sticking point, I don't think the low levels are the problem at all, as they don't directly contribute to the level curve. The large jumps between Mahogany and Blackthorn and Blue and Red could easily be solved by just... lowering their levels to match.
They are a problem in that they don't really allow you to grind against wild Pokémon after a certain point. Maybe not that much during the main game, but it becomes a big problem during the post-game as I talked about above. Lowering the levels of trainers could have fixed the problem, but I think there's an even better solution: raise the levels of the wild Pokémon. That would make things much better IMO.
That being said, HGSS did have shit handling of the could-be-amazing Safari Zone and completely ignoring the wild encounter changes from Crystal. The "level curve" is just an easily observable pattern gathered from looking at the levels throughout Johto, but it's basically a non-problem that doesn't affect gameplay nearly as much as the other shortcomings of HGSS that everyone ignores.
I agree. Think the level curve is not the only problem with HG/SS, and it is far from the biggest one. Personally, I think the trainer rematch system is the biggest problem with HG/SS, but others will probably disagree with me. These games have a ton of problems in total, and as I have said before, they are my least favorites for a good reason.
Sorry if this wasn't a good reply to what you said, but I felt that I had to reply here and this is the result.
And I am still not ready to post my other new unpopular opinion about HG/SS, it would otherwise have been a perfect opportunity to include it here. I'll get it done another time.