Are modern science fiction covers tasteless?

Not sure I'd call Chris Foss' work "tacky", but each to his own :)

One of the reasons why this might be happening (if it is) is that people identify that style with the genre, so publishers put something on the book that they know sells, regardless of how appropriate it is to the story. This can be seen in many other genres too where every book seems to have almost exactly the same book cover.

People buy what they're familiar with, if you step outside that you make it a lot harder for yourself. I'm not saying that's how it should be, but maybe that's why it happens.
REF: David M. Kelly.
You make a good point David, as with most things it all seems to boil down to what sells.
But I think people who buy SF probable have more open and adventures minds.
So I think the publishers should be a bit more open.
As for Chris Foss, I just got so fed up seeing his work everywhere back in the 70s & 80s.
And I do find his style a bit over the top, but as you say it's all a matter of personal taste.
You're right that Foss was probably overused back then (and the myriad imitators) and I agree SF readers are more open to new things, though I'm not sure the publishers realize that necessarily. There are definitely a lot of artists and illustrators out there who would welcome the work, so there's little excuse not to stretch the boundaries. I think a cover should always reflect the content to some extent, but many don't.
I think the quality ebbs and flows. I own many books and magazines from the 30's on and I can usually identify the decade that the book was printed at a glance. The quality was often a reflection of the success of the publishing house. Others tried to imitate a iconic or big selling title. The wave of Dune ripoff covers chased the books huge success. There were many titles that copied/imitated the Hobbit, Catcher in the Rye, The Fountainhead, the Foundation books, the juvenile Heinlein books, Star Wars etc. . Famous illustrators were copied, after Frazetta there was Boris and Rowena. After Michael Whelan there were numerous imitators. I find that I like certain covers throughout the history of Science Fiction and Fantasy. There are always knock-off and slapdash covers produced. Remember Sturgeon's Law, "90% of everything is Cr*p"

If you want really bad art look at some of the "covers" or art used for ebooks.