I think it’s down to management,
I’ve a relative whose conservatory is unusable, they always want you to sit in there too, in summer it’s suffocating, in winter it’s freezing.
However they only open the windows and doors when you arrive, or put the heating on when you arrive. It doesn’t habe time to cool down or heat up.
I’ve a friend where hers is used all year round, however she treats it like the rest of her house, the heating switches on with the rest of the house, so it’s always the same temp, maybe a couple of degrees cooler, the doors are never shut from the house to it.
In warmer weather she leaves the external doors and windows open from when she gets up. Literally she puts the kettle on then opens the doors and windows and leaves them like that till she goes out or goes to bed, She has those sort of string things over the door to stop things flying in. It does get warm but never unbearable, and if it’s that hot we want to be outside anyway.
So it is never able to fully have the heat build up in summer, or the cold take hold in winter, hence making it usable all year.
I get some folks don’t want to leave their doors open, or heat it, but i think that’s the trick. Her last house had a conservatory and it was the same, so in the twenty odd years I’ve known her, her conservatory has always been the most used room in her house.