I rent cars approximately all the time (I live on an island, so when I go anywhere, it's by air, and except for NYC, I always get a car wherever I go). Maybe 20 rentals/yr, a few years it was 50+ rentals.
Any of the big company "frequent renter" programs, like National Emerald Aisle/Executive, Hertz #1, etc., gives all the stuff you want. Usually I'm at airport locations (which do have extra taxes/fees), but it's "walk up to car, walk around one time just to make sure there's nothing obviously wrong, get in, adjust mirrors, configure usbc/carplay, stop at booth where they take my drivers license and credit card, drive off". With National I get my pick of any car on the lot (and with a corp discount code, usually around $30-40/day all-in).
The local branches suck a little more due to limited selection and lack of cannelized check out, but they're pretty close. Also way worse at most non-US locations (with the exception of big gateway airports).
I've returned cars and aside from one time where I drove over a concrete curb at CDG which I couldn't see (sigh, at the airport itself, returning the car), and had to pay for damages, it's always been painless. One time I returned a car where thieves at Stanford had broken the rear glass, and at SFO they just said "oh, another one", and checked a box on the return form; everything was handled via email after that.
There are also day-rate car rentals through Uber and some other programs like that where you use an app, find car, and drive off.
I would have no problem relying on rental for the last 5% of car needs (e.g. if I had a 2 seater or something, or didn't want to get snow tires to go into the mountains, etc. The "get to the rental location" is the biggest friction, and in true emergency cases where I absolutely need a car right then, which is why I usually rent for the whole trip.