Look, to my mind the issue is basically this.
Casters have more things
they can leverage. There's been a push back against the idea that characters should be looking at their character sheet for options in a pinch and should instead be (what I don't know? Sitting back and waiting for the muse to strike with creative inspiration?).
My experience is players tend to like things they can leverage. D&D has always been the most popular game and D&D has always been about looking at things for leverage. There's an OSR argument that this was not often the case in the early game, but to my mind this is nonsense. It's just that in the early game the main things you leverage were your equipment list: flasks of oil, ten foot poles, mirrors, bags of flour, caltrops etc. If you were stuck you looked at your equipment list to see if inspiration struck. (And of course your spell list if you had one).
Now this aspect of the game, and the kind of playstyle where such equipment choices matter has gone out of fashion, but it leaves a gap. With many classes the gap has been filled by magic and in some cases class features even those that are called 'ribbons' (which is a design that really reveals a certain design cluelessness and that WotC never really stopped thinking of D&D has just a tactical squad combat game).
For example this, according to Mike Mearls, is apparently a 'ribbon'.
Infiltration Expertise
Starting at 9th level, you can unfailingly create false identities for yourself. You must spend seven days and 25 gp to establish the
History, profession, and affiliations for an identity. You can’t establish an identity that belongs to someone else. For example, you might acquire appropriate clothing, letters of introduction, and official-looking certification to establish yourself as a member of a
Trading house from a remote city so you can insinuate yourself into the company of other wealthy merchants.
Thereafter, if you adopt the new identity as a disguise, other creatures believe you to be that person until given an obvious reason not to.
No. It's an ability you can leverage. Once you have it you can use it to do stuff. Things that can shape the whole game.
Now is it necessary for this ability to exist to do this kind of thing? No. But ready-to-handness matters in D&D.
Consider the following situations for old school play:
- I have a bag of flour written on my equipment list.
- The equipment list has 'bag of flour' written on it.
- Flour presumably exists in the world as bread exists.
Now, which player, assuming they've never heard of this trick before, is more likely to come up with the idea of revealing an invisible monster by throwing flour at them?
I think the answer is self-evident.
Casters simply have more things to leverage and more things to make a plan with. OSR misconceptions aside, things to leverage are aids to creativity not blockers.
Now add to this that skills in 5e are pretty bad and unreliable. They're not really meant to be your main articlces of leverage. This is by design, even if not necessarily articulated. Because D&D is not the game where you just do things. It's the game where you leverage the resources that you have, be they spells or equipment (Or magic items).