"I've always felt slightly resentful of this whole narrative of the importance of space and time to "think" and "be", because its very much a privileged position to be in."
I'm a single parent, and try to make time for myself, when I can, even if it is just an hour a day of watching a show I like, reading or playing games on my phone.
I think of reading, for example, as a mostly constructive, and good for the mind. Even gaming can be excellent for developing basic logic skills, memory, spatial awareness, keeping in touch via a pandemic etc.
I think if you're the sort of person that likes to feel like you've accomplished something, that's all well and good, but if you have a different idea from some, of what you consider a worthy way of passing the time, you shouldn't judge or try to impose how you feel on them (like they shouldn't with you).
It does read like you could do with relaxing a little though. Some tlc, where you make time, to "think" and "be" or whatever you fancy. Put the kids to bed an hour early, take a day off all housework but for one load of laundry, or whatever else you need to, then dedicate that time to something you really enjoy, but would normally be too busy to do. Then, if you like it, try to make that time, a part of your routine.
I like listening to podcasts or music while I do chores, as with those I do get the guilt of "I could be doing some constructive multi tasking, instead of just laying here lying a beached whale". Some tasks I really struggle with, without something to listen to, that's when I get "bored".