People like the OP want a game they are forced to relevel from level 1. Forced to replay the game from the start.
Even if the leveling experience was only ten hours people like the OP want this to limit them from being able to just give their character all the new abilities they want to try.
I have a question for you though OP. Does Tetris have a clear ending?
It does have a max level, you can achieve that max level in about 30 minutes if you are really good. So what purpose is there left to play? Maximum score? Even if I hit that the game does not end.
So why do people keep replaying Tetris? I only ever made one of any particular class in D2, and I still load up my character now and then to go and slay everything in Hell difficulty? Why should I do this.
Game Developers should have always focused on keeping a player playing the game, no matter what the level their character is. Not focusing on making a player replay from level 1 to get back to the maximum level.
Players like you OP, are not looking for a hard game, you are not looking for a replayable game either. Players like you OP are looking for a punishing game. Which you can deny as others have in the past, and that's fine. But it is what you want, you want to be punished for playing the game if you do it wrong.
But when developers start doing this method of game development they usually start being lazy about another important element, the ability to keep the player playing. If you make a game that keeps the player playing the game, even if there is no requirement to restart from the beginning of the game, then you have made a truly successful game. If you have made a game where the player "Wants" to restart from the beginning of the game not by requirement, but by choice, and "Wants" to keep playing the game when they reach maximum level. Then you have made a phenomenal game.
I am not every player, but I think I speak for a large majority when I say. Diablo 2 was a great game, it is a game I spent hundreds of hours on playing, but it's system that requires you to restart from level 1, was an archaic, punishing method of replayability.
Just because a game is good, does not mean everything was done in a good way. It just means you were willing to overlook it's flaws. I liked Teenage Mutant Ninja Turtles for the NES, that doesn't mean that it's flaws are not fatal design errors in todays gaming community.