I have not used one of these so my 'meh' vote is a bit uneducated. I do admit it looks interesting for signal wires (I would not use them for a high current wire). Maybe if I tried a few I might change my mind.
The thing is, I don't use butt connectors very often When I can I will replace the whole length of wire rather than do a but connection. (Admittedly there are times where that is impractical and a butt connector is called for, but it does not happen often in the projects I do.) I just did a *very* brief search for the equivalent for lugs or ring terminals and did not see any..... but that may only mean I did not look hard enough.
I’ve tried these and the biggest issue is not the sleeve itself, it’s damage to the insulation of the two wires where they enter the sleeve. A little too much from the heat gun and you end up with a mess. Then there is the question of the solder joint — is it fully wetted? Hard to tell under that foggy plastic goo.
I have used them for low current applications. I never use butt connectors. As an electronics technician, I can tell you a crimp, as well as a solder connection, is just designed to keep the copper conductors connected. A butt connector does not do that as the copper does not contact.