Any estimate on how much would the trip have cost? Just Interrail price
The in southern Europe (e.g. France, Spain, Italy), required seat reservation is most common and most expensive.
I don't mind requiring seat reservations, but that it is separate from the ticket price and significant (eg 15€/seat reservation in Italy), feels like price gouging. It also feels different from say the optional (and way lower priced seat reservations in German ICE's (high speed rail)). I rather pay for a "high speed rail supplement" instead of seat reservation haha :).
I interrailed last year through Germany, Austria, Slovenia, Italy and Switzerland.
In Germany I was lucky, I only had a small delay on the way back.
Austria was exceptional in everything. On time, modern trains and facilities. I guess the food on the train was expensive and bland, but I've never seen a train where that's different.
Slovenia was the weirdest and had the most delays. Train cars for which I had seat reservations consistently didn't exist or arrive. They use old stock, but that also made it kind of fun and there were great views. I couldn't rely on the time table though.
Italy has lots of high speed rail, but required (paid) seat reservations. The problem is that for almost any medium-long distance there's no slower speed alternative. The normal speed stock is fine (can be taken to go to smaller cities) and was generally on time.
Trains in Switzerland are exceptional too. Funnily enough, I did have fairly significant delays 2/5 times.
One has to add that most of the time when you buy a single ticket in Germany you have to (pay through the nose and) buy a ticket that is good for one specific train. Miss that train and your ticket is gone. This used to be different before the reform of the Deutsche Bahn after 1989; you used to buy a ticket for a 'communication' (connection between endpoints), not a specific train. TBF in like up to 200% of all cases Deutsche Bahn will route the wrong train in the wrong direction to a wrong station hours after the schedule in which case your Zugbindungsfahrausweis will fall back to work as a pre-reform ticket valid on all trains in that direction (sometimes even including an upgrade if an ICE is all there is, I think).