BookBarbarian
Expert Long Rester
I know the OP is going a different direction, but I really think AiME did a great job of removing the spellcasting system from 5e. I also really like how Audiences and Journeys expand the Social and Exploration pillars to fill the gap left by the absence of spells.I love gritty, low-magic settings. I love the sword & sorcery genre. I've played and run low-magic games and done some work on low-magic rules. I also love 5E.
That said, I'm definitely agree that 5E can't do it without serious rework. You really need to scrap the classes almost entirely. While not perfect, I would start by looking at what AiME did.
The core mechanic and numeric scale of 5E is absolutely conducive to a low-magic style, it's just that everything tacked on top isn't applicable. The default "setting" of 5E, while maybe not "high magic", is most certainly common/plentiful magic. Magic touches almost everything, included the rule systems. It's implied everywhere.
I think it'd be pretty easy to file the tolkienness off of it and have a great Dark Ages campaign.