Just putting it out there:
There are legitimate situations where a person might not be able to provide adequate alt text, such as cognitive disabilities, unfamiliarity with the language, or being blind/low-vision themselves, among others. Asking for help in those situations is fine.
If you can provide alt text but choose not to because "I don't even know how to describe this!" (except you're being hyperbolic, you do understand what you find salient about the image, otherwise you wouldn't have posted it), you are kind of being a jerk.
For example, I knew someone who posted a picture once, in an online community that required alt text, that was captioned just with the name of a location. People rightly took issue with this, because that implies a neutral photo of the location, when the salient detail was the massive flooding present in the image. But this person's reaction was "I don't even know what to SAY" and deleting the image in a huff, rather than acknowledging that "big flood" would've been a more descriptive two word caption than what they'd provided and people were not expecting them to write a damn novel.
Anyway, today I saw images where someone explicitly said they wouldn't provide alt text because they "had no words," implying the images were emotionally remarkable, and yet even as a sighted person I couldn't tell you what was alarming about the images; they looked entirely nondescript. Frankly alt text would've helped me know what I'm even supposed to be looking at.
Like, can you think for a moment from the perspective of someone who now knows that you're not telling them something relevant on purpose, and would reasonably feel insulted or upset?