For UK travel it depends a bit I think - a daily commuter's experience will be a lot different to that of somebody who is making off-peak leisure trips. For the latter my experience is that there's rarely crowding (especially in these pandemic times!) and that advance purchase (fixed to a specific train) tickets are often pretty good value.

(Writing this on a train from Exeter to Dawlish. The sleeper train from London to Penzance is good if you like that kind of thing.)

> it's usually very crowded and unreliable but it's also ruinously expensive

Given there are many alternatives - including coach (national express + megabus), air, driving, and not going at all - in addition to competition on many lines (for example you can do Manchester-London in first class at high speed for £500 return, or you can choose to pay £45 return and spend an extra hour traveling), it can't be that expensive.

> British rail travel in general is about as comfortable as pulling teeth with rusty pliers

A reminder to foreigners that this should be read assuming typical British self-deprecation.

Trains/carriages (so seats, noise etc) in Britain are usually of lower quality than their closest competitors in nearby countries (France, Germany, Netherlands, etc), and outside south east England they're also more expensive. However, they are generally more frequent, and the system as a whole is the safest in the world.

With London being so large, there are some commuter/suburban rail routes that cover significant distances, like Bedford to Brighton. I wouldn't choose to travel that route for the sake of the journey, but Høje Taastrup to København H on the commuter train is also less comfortable than on a regional or intercity train.