FWIW I just ordered a bunch of shit from home depot, it arrived faster than amazon could deliver it and everything I was looking for was in stock. I've also never had any major complaints in person with unhelpful staff—just the opposite. My only gripe with them is the self checkout you mentioned (why am I doing the store's work for them?), which certainly is not going to improve if Amazon moves into the retail space.
I have no clue where this impression of competence on Amazon's behalf is coming from—I must simply have radically different luck with the service they provide.
Perhaps it's different with a store like Home Depot where products are much bigger and perhaps harder to scan, but do people actually dislike self checkouts?
"Doing the work for the store" seems like such a non-argument to me. I would much prefer to scan things myself as I feel I can often do it faster, and I don't have to wait in a line if the store only has two cashiers staffed at a certain time.
You pump your own gas. Why is checking yourself out so much more controversial?
One possible reason is that eliminates a whole category of unskilled labor? (full disclosure, writing this from Oregon, where we can't pump our own gas to preserve another category of unskilled labor jobs - except right now, thanks COVID-19?) I personally would probably prefer to have a human checker for that reason, I don't notice much improvement in speed or ease of checking out when I do it myself, there's just a line for the self-checkouts instead...
The "pro desk," garden center, and the returns desk are all places where I am able to have someone check me out. As you said, I don't work for Home Depot. However if you're getting penny clearance items the self checkout is the place to visit.
I have no clue where this impression of competence on Amazon's behalf is coming from—I must simply have radically different luck with the service they provide.