Citation needed. Old rougelikes/rougelites are designed to optimise for subjective fun, which naturally translates to more time spent. If something is fun, it's obvious that people will keep playing for longer. What's wrong is using dirty psychological tricks to bypass that and go directly for increasing the time spent on the game.
Also, I've not come across many roguelites which have a strong RNG component in their progression path. Roguelites are inherently random but their progression mechanics are generally quite regular on any given playthrough. All the ones I've played you progress quite linearly just by playing the game, not grinding for a chance to process. The worst I've heard of is one FTL's ship unlocks which involves getting two or three good rolls in a playthrough, which players (mostly 100% speedrunners) do complain about. Certainly nothing to the level of what is very common in lootboxes (where a massive grind for a less than 1 in 100 chance is common).
Games with RNG-gated content have a strong incentive to make progressing take as much time as possible, because the more time it takes the more people play the game, and the more people play the game the more they'll naturally advertise it to their friends.
>Games with long progression paths have an incentive to keep that process as interesting is possible, otherwise people will just stop playing (and along the way the player is having fun).
Games that ask for money also have an incentive to keep that process as interesting as possible, otherwise people will also stop playing. Just because you're asking for people to spend money it doesn't mean that you can magically make a shit game.
They have an incentive to make the path where you're paying as interesting as possible, and make the path where you're not as painful/boring as possible (while dangling the idea of the interesting bits in front of you)