Skeptical about "observer effect" for double-slit experiment

If you don't know what it is, here is a brief explanation of the mainstream view:

https://www.youtube.com/watch?v=Q1YqgPAtzho

What makes me skeptical is that the observation of the particle is always described in vague terms. Everyone I have heard speak about this, from this video, to popular physicists, to my professors in school always talk about "watching" the particle without explaining what they mean by "watching". What is the experiment they did to "watch" the particle, where it behaved like a particle when they "watched" it, but like a wave when they didn't watch it? For relativity, everyone knows about the Michelson-Morley experiment, and the details of how they made the interferometer to test this. So why is it that for the double-slit experiment, the details of how they "watched" the particles is never discussed? And furthermore, why can't I find any videos of real-life demonstrations of the "observer effect" on youtube? Honestly it seems like bullshit to me.

Even before entering the discussion of watching the particle, what IS a particle? Has anyone ever seen one?

"No evidence for particles": https://arxiv.org/ftp/arxiv/papers/0807/0807.3930.pdf

Yes, sounds like bullshit.  This is why scientific papers have a "methods" section.  Without that, one can't judge the paper.

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Allen wrote

Using it to confirm relativity is like blaming the failure of any experiments to get expected results on evil magical elves and then using failed experiments to confirm the existence of evil magical elves.

I thought the same thing when I first learned about it. It seems strange how people seem to think that since Michelson-Morley failed to prove X, this means that theory Y is true. Seems like platonic shenanigans.