I don't think it would be controversial to say that "useless" is way too strong a term for describing shortcomings of computers.
I can't find the quote's context either, but consider this - why would someone ask Picasso about computers?
If the quote is correct, I wouldn't be surprised if it was in response to something like "Do you believe that computers can [be made to] create art [on their own]?". In which case the quote becomes much less categoric.
This is our monthly thread for collecting these little gems and pearls of wisdom, rationality-related quotes you've seen recently, or had stored in your quotesfile for ages, and which might be handy to link to in one of our discussions.