What's the point of 9999 levels in Disgeaa if the stat differences are so little as to allow such a meaningless number of levels? You may as well crack open Progress Quest at that point.
Well, at sufficiently high levels, the difference between levels may be small, but you're not getting those levels one at a time. You can easily gain dozens of levels with a single action (that kills multiple enemies, since unfortunately only kills get you XP), or even hundreds if you're a level 1 character with a powerful weapon using Winged Slayer (which you have because you reincarnated after learning it) on Cave of Ordeals 3.
In later games in the series, I hear that you can go from level 1 to 4-digit levels.
Then again, the whole level system feels meaningless once you realize that the way to get high stats is to levelup your equipment instead; such powerful equipment is why a level 1 character can one-shot Cave of Ordeals 3.
By the way, random Disgaea fact: Level 99 enemies give a lot of XP. In fact, for an enemy that isn't level 99 to give that much XP, the enemy would have to be over level 300. On the other hand, enemies that are level 100 or just above that give rather poor XP when compared to those just below 99. (This quirk also applies to other N1 RPGs (the ones developed by N1's Japanese branch, not other games by that company).
And the Avernum remakes are hardcapped at 30, if I recall, with a maximum of skillpoints to spend too.
That's one reason I would rather play the "originals", where you can get as many skill-point boosting potions as you want. In Avernum 1 and 2, you just need to buy out the shopkeeper's inventory, and the inventory will restock, and there's someone who sells those potions. In Avernum 3, it's possible to make those potions, though the required recipe is treated as an artifact in terms of rarity (in other words, getting it requires a special quest).
My preference is to make sure levels have diminishing returns in numbers so a player might grind out tons of levels all the way to 99, but it doesn't get them as much as the game's expected 1-50.
Earlier Dragon Quest games, particularly 3 and 4, do that (though 40 is around when you'd beat the game, though I've casually beaten DQ3's remakes at lower levels, before learning the spell that heals the entire party).
But games should absolutely have level caps. None of that "infinite" crap like Diablo 3 supposedly has. Every game MUST have an ending point. Not having one is very disrespectful to the player. The best part of Grim Dawn is reaching level 100 (cap) and firing up a new character of a different build!
So, you'd say that a game like Cookie Clicker is disrespectful to the player due to not having any cap on cookies or other things you get in the game?
(There is a point in Cookie Clicker where you run out of good ways to boost cookie production, so things slow to a craw with your cookie production no longer seeing exponential growth.)