I feel like this question almost needs to be broken down into multiple answers.
While watching TV all day every day wouldn't be a very good thing, I do think that people tend to devalue activities deemed worthless, like TV, without realizing that even that is learning, or leads to learning. I can't count the number of times TV shows or movies have sparked Google searches on historic figures or events, discussions of tropes and archetypes in storytelling, the breaking down of harmful stereotypes and discrimination in shows... While TV watching can be something passive, it can also be something very involved, something that leads to lots of thinking, creating of stories (fan fiction is the way a lot of young writers first get into writing!), and interesting discussions. Once you start actually looking for learning in everything, not just thinking of it as something that needs to be deliberately imparted to young minds, you start seeing it everywhere.
I also think people don't full respect the power of boredom. Watching TV all day every day is going to get boring. It just will. And then they'll be looking for different things to do.
|Though admittedly, if I got the food network I might just watch |
TV all day every day for at least a week or two...
Another important thing to keep in mind is that unschooling parents are not supposed to be in a passive role. It's not like unschooling parents just say "okay, go learn now!" and then proceed to ignore their kids. There are times when kids definitely need their own space to learn and explore, but there are plenty of times they don't. Parents can sit down and watch those shows, initiate those conversations and Google searches. Parents can also provide a wealth of interesting library books and board games, suggest activities and clubs and outings.
Which isn't to say that worries about a child spending tons of time in front of a screen aren't things parents who are unschooling sometimes have trouble dealing with, especially when they first start transitioning to unschooling. Deschooling is an important part of unschooling if you're going from either school or very formal/strict/school-at-home homeschooling, so it's important to leave time for that adjustment to a very different lifestyle. What unschooling looks like when you first start is almost certainly going to be very, very different than what it will look like a year or two later. Along those lines, don't give up too fast! Just because it doesn't seem to be "working" right away doesn't mean something is wrong, it probably just means your child(ren) are adjusting to not having to "do learning."
For specific situations, experienced unschooling parents are going to be much more helpful than I could be, not being a parent myself so never having been on that side of things. All I'm saying is that such a worry is often unfounded, and also that there's a whole lot more to it than just "what if my kid just watches TV all day?"