On one hand, I appreciate beautiful cover art and enjoy striking and imaginative design, especially when it's attached to books I read and buy. On the other, I read and buy Baen books, which are … notorious for having the latter elements, but not in a good way.
So while a nice cover is certainly a bonus and will draw me to look at something I might not have previously (I've certainly tried a number of new authors based on their having netted a Tom Canty or Jody Lee or Bob Eggleton pic), I don't consider it a deal-breaker if the cover is bland or sometimes outright bad.
Of course, I don't see the stuff when browsing through the listings on my Kindle.
Though I must say that the combination of tacky Poser-looking 3D "art" and poorly positioned ugly fonts so common on fantasy backlist e-book re-pubs is a definite turn-off and it takes an author whose works I'm already acquainted with or has a good reputation otherwise to overcome that stigma.
As for generating your own generic cover, I say make up a template in something like Inkscape
, or similar vector tool using a nice, non-system font. You can then just adjust the text and tweak the colours for each book and maybe add a picture in the background.
It may take a couple of tries until you have a reusable basic layout you're satisfied with, but after that you'll be able to generate plain but appealing covers like the ones on the B&N/Collins/Penguin Classics lines, which are mainly big blocks of solid colour with a little vaguely representative artwork to distinguish each title but have a formulaic but pleasant look and feel.