There's "I want to write but I genuinely have no idea what to put on the page", which is different from "I do know what I want to write, but it feels dumb and I feel dumb writing it down". People feeling like the latter may act like the former because they're too embarrassed to talk about their dumb-feeling ideas, but they are distinct issues XD
I mean, one way to not get writers block is to not be too attached to 'being' a writer and just not care about writing when you don't have inspiration
Is that 'waiting for inspiration'? It's definitely a different mindset than actively waiting for inspiration and getting frustrated when it doesn't strike :'D
But what if you have planner's block and can't think of a plan? 
I actually find inspiration strikes pretty often when I'm watching a show or browsing the internet, and it does let me daydream provided it's pauseable.
But I get it's distinct from being in a situation where you're forced to think about stuff to keep yourself entertained; I'm not sure I'd call it daydreaming though, it's a very deliberate process for me (e.g. when I'm lying awake in 'bed', I'll deliberately focus on thinking about my stories so I'm not bored while waiting to fall asleep) whereas to me 'daydreaming' has connotations of your mind wandering off without your permission (which tends to happen in the middle of something that requires my attention because fate is vindictive :P)
WDNOS: Writing Disorder Not Otherwise Specified
But yeah, I feel like a lot of people who say 'X is not real' is just objecting to the term used, whether it be because it's an umbrella term that doesn't actually specify anything, or for some other reason. X is always real given some definition of X; like, 'things that cause writers to struggle to write' clearly exists lmao
'X is not real' is just a particularly blunt/shock value/arguably invalidating way to put it :'D
I think a useful conception of 'writer's block' that's not covered by burnout/lack of planning/self-doubt/the other things people have mentioned here is a 'slow period'. Sure, not writing is a choice and you can technically always write at will if you chose to do so, but it's just not the case that people can consistently output meaningful/inspired writing at will, no matter how well-rested/confident/prepared you are.
There is a very real difference between someone writing stream-of-consciousness gibberish just to force themselves to write, vs someone who started off forcing themselves to write but is falling into some good momentum where they're actually thinking about what they're writing and solving problems in their story, vs someone in a fit of inspiration with ideas bursting forth from their mind that they're very excited about. There WILL be moments when you're the former person, and I think it's fair to call that 'writer's block' 