I think it's more important what they are watching than how much they are watching.
Stick on some numberblocks etc or educational programme. No different to a teacher standing in front of them. It's still someone standing there talking at them at the end of the day.
TV is better than tablets etc as its not right in their face and is more social.
Cbeebies is great and varied.
Stick on song of sounds which is what they do at school.
We put on bluey the floor is lava on YouTube on the TV. And there's a few games people have recorded and the character runs and jumps and they copy it and pretend to be the character. Same for just dance. We have it on the switch connected to the tvm or if it's being used we do the same as the bluey game but a ore recorded just dance.
Jump-start Johnny exercise for kids.
Literally limitless oppertunities and things to do which doesn't numb the Brain.
It's knowing how to use it.
My older two, (9 and 10) love documentaries. Loads on Disney and netflix and YouTube.
As long as it's not YouTubers playing roblox etc then I don't limit it unless arguments are happening. I let them watch you tubers if they really want to once or twice a day for 20 minutes or so