Such wibble. If you want to travel on a puffer you follow the rules of the provider or don't go. These railways need your support. Go, even if you have to follow what in your view are silly rules. If you dont go now they wont be there for you when you do want to go.
We have been on two very different preserved railways recently: NYMR and Avon Valley.
Both ran very similar arrangements: You book specific seats on specific trains and travel the length of the line. You wear a face mask when moving around inside or on the train but not at your seat. I kept mine on whilst on the platform as it was easier. Catering was available on the trains, shops and cafes were open. The toilets on and off the train were open. Both railways offered a choice of compartments or tables. It was quite easy, relaxing and enjoyable. Both trains we went on were well loaded but the NYMR services were less busy than I would expect ( although it was a wet day)
The NYMR actually ran two trains. A Pickering > Whitby "express" that didn't obviously pick up at intermediate stations and a "local" Pickering > Grosmont that did
Were there some additional rules? Yes. Could you run around as if you own the place? No. It was
slightly different to "normal" but not inconveniently so. It is a bit of PITA to book in advance but it is hardly hard. if you cant cope with that the modern world will be hard work. We had a nice day out and hardly noticed the covid rules. You could even stick your head out of the train!
BTW: I am an English Heritage member, I didn't know they ran trains