In my opinion, that's a personal opinion.  If one values rigidity in a plan over spontaneously enjoying whatever ATC is online, then I suppose that could be a valid argument.  However, many thousands of people, including many hundreds of Europeans, fly happily in the US every day.  To each his own.

I would not describe this as 'rigidity vs spontaneous enjoyment'.  I would describe a schedule as predictable for planning purposes, instead of chasing ATC all over the place, only to have it shut down as you're ready for taxi.  Now that's enjoyment!  And I would not describe it as either/or - you could have some ARTCCs that have a schedule periodically, in addition to the published events.  I do find it frustrating at times when I want to practice and use ATC and it pops up and goes away before you can use it.  Having some degree of predictability would be very helpful to many pilots; Europeans and otherwise.