So yeah I should have been more specific, as I had foreknowledge of Wilshire's experience with the games in my comment. Certainly I would always suggest to a new player to play the games 'as intended', and no doubt there is a persistent sense of reward after overcoming seemingly impossible enemy or boss encounters (which then end up seeming like a cakewalk the further you get into the games).
That being said however, I do think that once someone has familiarized themselves with the game enough and are into it but find themselves frustrated by certain things -- in particular, the run back to the bosses -- I don't at all discourage/admonish someone for just relying on summons or co-op to ease their way through. The boss runs are easily my biggest issue with the games (Souls/Bloodborne anyhow, haven't played Sekiro yet but it seems they mostly fixed this issue by putting the 'bonfires' or whatever very near or directly beside the boss). But in the Souls games and even Bloodborne I truly think the 'boss run' element is a flatout bad design choice. It made sense in Demon's Souls the most, but it feels like something they just carried over into the Dark Souls games mostly arbitrarily. It is a pure time-waster, and seems to me like one of the few examples of just plain 'artificial gameplay', and I've lost count of how many times I've heard of other people (myself among them) getting burned out specifically because of this aspect.
So yeah, I totally would suggest people try beat a boss solo or whatever at least a few times, even if just to get an idea of their attack patterns, but I also would ALWAYS prefer that someone be able to experience the vast wealth of content (especially if they're into the story aspects) in these games even if it means doing a save-state cheat to let you respawn in front of a fog door. Hell, even if FromSoftware just made the mandatory bosses have respawns occur no less than a minute away and with no or minimal enemies, while keeping side-bosses (of which there are always a crapload in these games) with the more traditional 'boss run' element, I think it would make a big difference.
I have no problem with a game being challenging but it needs to be justified, and it should never be a pure time waster...which in many cases is what the boss-runs end up being (inevitably, really -- once you know the 'route' and just run past the enemies, it's not even a challenge -- it's just a mindless dash that can frequently take 3+ minutes, not counting load times or whatever else). The games have plenty of challenges to overcome and deliver that rewarding feeling, and I really don't believe anything is gained by forcing this extra layer of punishment onto the player.