It's not a full replacement, but it's the one you already have.
Who knows, maybe the counterfactual isn't "wrote a concise doc," but rather "didn't share the information at all," in which case I suppose Loom et al is a positive.
Before that you got an issue saying "There's a bug on the notification list" and you needed to figure out how to reproduce it. Now you get a video showing exactly how to reproduce it.
It's a life changer and the opposite of what you describe.
This hasn't been my experience; if anything, quite the opposite, in that it's enabled my team to contribute much more actively to design. The effort of providing actionable feedback is admittedly slightly higher, but that's not a bad thing; needing to (and having time to!) write up feedback seems to yield more actionable results than doing it verbally in the moment, and for things that do really need talking through we have several sync touchpoints during the week with our embedded designer.
Of course, in contexts where no such touchpoints exist or where design and eng generally don't have a close relationship, I could see Loom being difficult - but I'm not sure I'd blame that first on the tool; if Design and Eng communicate only by throwing things over a transom at one another, I think the tool much more likely exposes problems you already had and didn't know about.
It's not (yet?) heavily used among engs where I am, but we love it anyway for massively shortening the feedback loop with designers who can drop a 30-second demo of some prototype UI at the head of a Slack thread and asynchronously receive the kind of nuanced feedback that'd usually need to start off with a (necessarily synchronous) huddle.