Not really, as you're still saddled with all the spells and extraneous stuff that druids come with, you're also still limited by size and type, these restrictions would IMO, fall away as you gained levels (which they don't for a druid) so in place of spells you can become small or large, eventually tiny and huge. Plus you've got all those ties to nature and stuff, which would need to be done away with.
Sure, you could make a shapechanger druid, but it would be such a heavily modified druid that it might just need its own class.
That is all true, and I can't *really* argue against that. But I'm not sure I'd want that.
A dedicated shapeshifter is one of those things that sounds could and could theoretically exist. It wouldn't be *that* hard to balance, replacing the druids spellcasting with set transmutation spells from various spell lists and abilities of similar power. But it's one of those ideas that doesn't have a solid history in the game and isn't super archetypal in fantasy.
There's certainly some examples. Skinwalkers in
Dresden Files spring immediately to mind. But they're not as ubiquitous as the fighter or the rogue.
Ideally, classes should be big tent ideas. Things designed to fit into almost every world or setting (with minimal changes) or campaign. Things that you play from level 1 to level 20. Each with a variety of subclasses.
Smaller, niche ideas should be lumped into subclasses. Or, theoretically, prestige classes.
This would be easier with 3rd Party Products or an OGL as there could be world specific classes and content. Stuff like a "shapesmith" class could fit nicely in that paradigm, and belong to a world where shapechangers are as important as mages and thieves.
There's LOTs of cool ideas that could theoretically work as classes, but that I'm not sure warrant full official treatment in a splatbook. There's almost an infinite amount of neat new mechanics or bits of flavour that could be worked into a class.