For me it's not having to wait at the carousel at the end, it's having to wait in that enormous line at the beginning. I really don't understand why they make it so much work just to drop off your checked bag before the flight.

Many European (and other) airports now have self-done baggage drop-off.

At Copenhagen Airport, I usually get off the metro, walk to the luggage tag machines at the end of the platform and scan my passport (or boarding pass). That prints a bag tag (and boarding pass if requested), so after sticking that to my luggage I drop it off at the counter — I put the bag on the scale/conveyor, it scans the barcode, prompts me to press "Confirm" that there's no explosives etc, and I'm done.

I scan my boarding pass to go through the barrier into the security screening, walk to the gate, and very often scan the boarding pass again to get onto the jetbridge.

I can easily go from the metro to the plane without interacting with anyone. I understand this is Scandinavian bliss.

(Exceptions are trips to countries where I need my documents to be checked; e.g. to go to the USA a checkin agent has to see my ESTA visa waiver. Oddly, going somewhere like China which requires a printed visa in my passport does work on the machine, as the machine prompts me to scan it.)

My experience with United over the past few years is that there's a pretty quick pre-registered drop line. But that doesn't apply everywhere presumably. I rarely check bags but for some types of trips (generally hiking trips for me) it's sort of unavoidable.