Has "Assisted" dumbed-down contesting? - I'd say, no - it is just another technology advance that allows the really skilled ops to do a lot better and still beat the lesser skilled ops in the assisted category.
Now, if you had asked "Has "the globally interconnected packet spotting system and the Reverse Beacon Network" dumbed-down DXing and if so has that dumbed down contesting in any way" I'd say yes, definitely.
Poor operating in pileups has been complained about at least as long as I've been licensed (1969) and really for many decades before that. But, when individual packetclusters began to be interconnected over the Internet and when general purpose logging software integrated spotting, it seemed to quickly get exponentially worse.
The Reverse Beacon Network showed an immediate negative impact: skimmers don't report if a station is working split, so when "DX P5ABC 7.007" comes out, hundreds start calling on 7.007 and the pileup police startup, and the downward spiral starts up.
Contest pileups are much thinner than rare one DX pileups, and there is almost no split operation, but when human spotters and skimmers make mistakes, a busted spot leads to many callers causing a dupe deluge on poor SP5ABC, who they already worked!
You could have also asked "What has really dumbed down contesting?" and my answer would be history files - ops are using autofiill on name, state, CK, PREC, etc and not even listening to what is actually being sent.
I live in Maryland and have for many years, but a few years ago I started remote opping a station in VA. In contests where MD is the exchange, 30% of stations logged me in MD even though I was sending VA, when the norm was less than 10% busting the exchange if I was in MD and sending MD.
Looking at those calls who obviously were using history files and not overriding them with actual copying, I never saw the callsign of anyone who finished in the top ten in any category. The great contest ops are using the technology skillfully vs. in a dumbed down manner!
73 John K3TN