Extra Credits made an episode on Souls actually already having easy mode. You just use spells or bow and that really simplifies things for you. By adding exploitables skills/items/tactics devs can let people decide for themselves how challenging the game should be. As a slacker kind of player I appreciate that.
Honestly, I never liked this method that much in any game when it's done. Like, if the item to do so was something that was locked away and required effort to get like the Temmie Armor in Undertale, that's at least a little more okay since it means you have to go out of your way for something exploitable. But when that exploitable thing is just given to you for free, it throws off the balance of a normal playthrough enough that it becomes disappointing for higher level play, which extra hurts if the said exploit isn't fun (which most of the time, it isn't). It becomes "Why not use X exploit?", and while you can always purposely limit the speedrun/playthrough to cater to such specifics, stipulations like that have always been lame as a concept in general (see complaints about Competitive Smash), and the feeling of having your other tools be almost if not exactly as strong has always been way more satisfying as a gameplay experience.
Or at least, there is a difference when stipulations for challenge feel forced from players rather than something designed/allowed from developers. A low level run in any Final Fantasy, while fun, is usually just tiring as a concept for how many hoops you have to go through to make it work. In contrast, the KH series with the EXP zero ability feels welcome, especially when they give nice bonuses that fit to make it a good experience (KH2 EXP zero/Critical Mode is great, BBS and KH1.5 EXP zero is awkward since it gives you too many bonuses).
To sum up, if a dev puts in an exploitable item that I
have to get, I feel compelled as a player to think "I guess I'm
supposed to use this?", and it feels lame when I have to go out of my way to avoid it. In contrast, it feels better if the exploit must be earned/locked away, so I think instead, "Oh, maybe I'm not supposed to really use this?" if I have to go out of my way for the exploit, and doesn't hurt any normal/high level play.
Shovel Knight's phase locket that someone brought up is the exact kind of thing that I don't/didn't like to see. For a general playthrough, most of the relics are too specifically used and in general balanced very weak and way too specifically, which made 5/8 of them feel nigh useless to experiment with and as a result they felt very lame. Then you get Phase Locket, which is stupidly good that you can use it almost all the time for pretty low cost, or the Propellar Dagger and Dust Knuckles which round out the rest of the gameplay when there are no obstacles or only dust blocks in the way. Be it a speedrun or a casual playthrough, I find myself just always going to those for 90% of the game and by the end they felt like the only things worth using.
Plague Knight's balancing is far more ideal. Not only does it basically have the phase locket but slightly balanced to not be quite as good, but it reverses the tides where instead 6/8 arcanas felt strong and super useful at multiple times across almost every level. It was way more fun to go through any given Plague knight level and mess around with the powers because they all felt good and useful, instead of just 1 or 3 of them. When I played throgh Plague Knight casually not too long ago, I wanted to go back through the levels and figure out certain sections with different items because it all felt good, which is way more than could be said for my normal Shovel knight. As a result, watching any Speedrun of Plague Knight has usually been way more interesting than any given Shovel Knight run, and that's not including the fact that Plague Knight just has more interesting mobility; this is purely from the different item usage and the creative things that come up.
A different example I guess would be Kingdom Hearts BBS versus DDD. Keep in mind, both of these games put in ridiculously strong options for the player, but DDD goes overboard when it took an extremely strong spell with Mine, made it STRONGER while also taking away a lot of other super strong commands so that everything else felt weaker, making it feel like a staple even for a casual playthrough when the endgame toughness gets going. DDD is still fun since Balloon doesn't win you every fight, but the balance does not feel right at all in comparison, so it's a game a lot of KH players couldn't get into (beyond other reasons) and was a lot less fun to go back into versus BBS which was much more well rounded despite Shotlocks being stupidly good there.
tl;dr - If they were going to put in accomdations for a "super easy" playthrough, I'd rather something as obvious as an Automatic mode or Mario-esque level skips, rather than something thrown in that ruins the balance for other levels of play. Or, if they did go that route of adding in some exploitable item, it was something that in someway somehow felt separated from normal play so that it really gave the distinction of not being "normal".
VVVVV Eh, I don't like that either but that's also way more personal and my justification is a pretty weirdly specific, but that would be better than just putting it in normal stuff
