Hi,
URL format and length it's a ranking signal - that means shorter URLs are "more important" but only if there is a taxonomy in place. If all your URLs are directly on the root - then this doesn’t play any role. So if your domain has a lot of content and some or most is structured domain/folder/ and domain/folder/folder etc - then moving from /blog to the root will bring some signals that this content might be important.
But note that having short urls on the root directly it's not a roadmap to good rankings
On the user side - if the content is "blog related" - blogging, articles, opinions etc - then I would keep it on the /blog/ as it can influence the CTR in SERPs - that also depending on the queries of course and if it will match what users are expecting - a blog thing or some other resource ...
Hope it makes sense.
Cheers.