I feel like you're extrapolating a little. I wasn't really following social medias or forums back then so ultimately I have no idea how much casuals had a problem with it, but I suspect they didn't. To my eyes they were just enjoying the content and pressing their buttons in whatever way felt good to them. Which is still the case today, the main difference being that the game makes sure the lower skill level doesn't stand out too much, if at all.
I actually don't remember casual players complaining about it ingame, but I do remember some jobs having some stigma, like BLM had until very recently, about how difficult it is to play. MCH and DRK were two of those in HW, and it stuck enough to MCH for it to last until the end of SB (just check one of the old Larrysaur vids joking that you need an engineering phd to play MCH). I feel that it's unfortunately something that you'll never really shake of if you have huge differences in skill requirement between jobs in the roster like it used to be the case, even if people still played mch like garbage in casual content and went by just fine anyway. DRK actually, is the best example to my eyes because the job could be played with only half its kit without the hard parts which were tied to the Darkside stance: a lot of casual tanks just didn't use it, so they lost the 20% damage buff and access to some of the skills unlocked by it, but in exchange didn't have to deal with the hardcore MP management it brought.
I'm actually on your side however when it comes to job discrepancies. Every job should be accessible, but every job should also have an actual ceiling, all of them with unique gameplay and challenges. I don't like uptime, so I don't want to deal with the ceiling of such a BLM job, but I'm sure a lot of BLM vets would love this. A lot of people don't like hard rng triage and prios, but I love this and would like my ammo back. A lot of people miss managing resources and MP and want old DRK back as well.
Counterpoint: I've been in many a static where the problematic player was the SMN. Do you know why? They kept messing up because they zoned out. They were the kind of players that didn't want to engage with more challenging jobs to focus on encounter design (and they tended to be lazy af as well). But the job put them to sleep further. Anecdotal? Perhaps, I don't know, but it's been my EW experience with SMN players.
Accessibility all across the board, skill ceiling as well. Problem solved except for that layer of players that cannot accept that they don't have the skills to master something 110%.