Networking Gone?

I'm handicapped and my main computer, an iMac I haven't upgraded lately is in my office upstairs and I often use my MacBook Pro to network with the iMac so I can work and watch television in my front room, at the same time. Unfortunately, the latest upgrade makes the networking capacity almost useless. Instead of being able to operate the remote computer as if you were working on that computer, now when using Screen Sharing, it begins nicely, as it use to, but soon you lose control of the screen. At first you can move the cursor to move the view of the screen (my iMac has a large screen so I have to adjust the cursor to see different portions of the screen). Soon this capacity stops working, eventually the cursor becomes huge and won't move at all. It can be remedied by quitting Screen Sharing then starting again, but it is rather a pain in the butt to have to stop and reopen screen sharing every 5 minutes. The other way round it works fine. The iMac which is running Monterey controls the MacBook Pro screen just as it should. It's just the "upgrade" to Sonoma 14.3 in which the screen sharing doesn't work. I guess the question is, is there any other way to share screens in a network other than Mac Screen Sharing?