You are making the mistake of "playing scales" in front of an audience who expect a performance of a final composition rather than a teacher who can provide feedback on your work in progress.
Change the audience.
It is hard to stay motivated when the "wrong audience" is yourself.
There are many ways to learn to play music. If you just want to learn to play songs then do that. Don't worry about the scales.
Instead of learning scales start jamming with some background music. Start to transcribe some solo you like (don't use tabs) and learn to play that way.
If you aren't motivated by playing scales then you shouldn't do it.
Make sure that it's always about enjoying music first, then about learning theory or technique.
One of my favorite ways to learn scales was to do patterns in the scales over some chord progression. That ways I was playing little patterned melodies while learning to play the scales.
Also don't confuse learning scales with learning to pick. Most of the times when you hear someone learning scales just going up and down the strings they are really practicing picking technique which is many times harder than to learn the actual scales.
The most frustrating part is I used to be a section leader when I played clarinet in HS and could borderline sight read at that point. I've forgotten pretty much all my musical knowledge since then (including how to read sheet music), so it has been horribly frustrating to have shadows of memories for how fluent I used to be in this stuff and to have to start from scratch again. That probably makes me much less patient than I normally would be.
Your ear is the only thing thats really needed.
A year ago I was trying to level up my writing ability and wrote a medium-length article, with proper outlining, attempting to explain an abstract idea through concrete examples (mostly business related).
I sent it to one friend and was told "this is too intellectual, it contains no useful information, no-one will want to read it". No response to the actual subject matter.[1]
I was floored. I didn't want to be the stereotypical writer who gets defensive in the face of criticism, but my friend was so dismissive and patronising that it was hard to maintain my motivation. To rub salt in the wound they later told me "look, you just have to get used to harsh feedback".
[1] (Another friend read it and had some criticisms, but did actually engage with the argument I was making).
I write some pretty complex essays purely of things I find interesting. For examples this one https://medium.com/black-n-white/the-problem-with-problems-4...
Most of my essays are based on looser discussions I have with people which I then ponder over and distill down into an essay.
So I always make sure to send to those people who have a basic idea of what I am talking about. I.e. I am not trying to convert some reader from being completely uninterested in the subject matter into someone who should care.
Instead I send to the people I discussed it with or a few group of people I know share my interest.
That mostly steers me clear of any frustration :)
Another thing I try and do is think about my essays as a way to get thought out of my head and down on paper. That way whether tens of thousands of people read it as they sometimes do or no one (as they sometimes do) I can still check it off as done.