Its a popular archetype that, if doing it, people will ask for it immediately. The thing to remember when we're at this whole magical argument is that D&D is a high fantasy, high magic game where crashed space-ships, ancient ruins a plenty, time travel, space travel, planer travel, the works
I get people like the low magic, but, D&D has never really given itself to low magic at all and its going to lead a clash with simply how D&D is presented. Even Greyhawk, the one people try to present as the grittier, low-magic setting, is still the setting with the aformentioned crashed alien spacecraft. Trying to limit to 'this is just medieval-ish Europe (except with plate armor)' is a fraught game when Egyptian and Greek sphinges co-exist with Indian naga, Japanese tengu (which kenku are based on), Icelandic trolls and German kobolds
The problem is, druid shapeshifting is the archetype's Thing. The archetype is much wider and due to 'popular enough that D&D felt a massive pinch in its heyday' Warcraft, the shapeshfiter nature caster is the druid archetype. When people pick 'druid' they want "I will turn into a bear or werewolf and maul a dude", they don't want "You're wearing mail armor"
Clerics are, by their design, evocative of Chrstian knights going around and crusder-ing. They're the very people who wiped out the druids. They're what a druid would fight.
Warcraft's priest is a cloth-wearer who uses holy magic. Think White Mages from Final Fantasy (which sort of derive from the white robes from Dragonlance but went all in on healing and also harvesting your allies wounds for power to unleash the Blood Lily). D&D is really unusual in its healer class is heavily armored, and if redoing D&D today, Cleric would easily be the first on the chopping block simply due to the archetype not being a thing outside of D&D
The other problem of course comes from 'are we adding too much into sub-classes', which in turn makes sub-classes hard to design. Trying to merge Druid and Cleric into one class is a mess because the two classes want such different things in how they're presented that its going to mangle one or the other, or give them things that are useless to the class ideal.
I do understand merging, but over-merging can easily dilute what makes people drawn to particular archetypes. I'd argue that's the wizard's problem, being too over-merged into 'the spellcaster' in the past, which in turn is why warlocks and sorcerers have such popularity despite a bit of mechanical jank on the sorcerer's part. They're allowing the fictional archetype to shine brighter
Splitting stuff, making it more compartmentalised so they have a specific list of things they can do, could also benefit the gap by limiting what any individual caster can do, rather than the current 'wizards can do anything' casting at the moment