As for his influence on the wine world in general, I would say that there's less outright crap around, but that quality is rising to a kind of uniformity that discounts and undervalues those styles that Parker dislikes or simply doesn't get. Of course, I personally much preferred things before such critics had risen to their present level of influence, since great wines were much cheaper and yet it was still fairly easy, as an individual, to make a lot of money out of buying en primeur and selling later. These days, unless one is one of the fortunate few who have the right contacts, one can pretty much forget about getting allocations of great Burgundy in good and above vintages, and a lot of Bordeaux en primeur merchants insist that if one is to receive a case of a 1st growth, then one needs to buy a "spread" of lesser things too. This hasn't happened to me, but I've seen it happen to others, so I would also assert that the colossal number of persons seeking these wines, be it to profiteer on or drink - as well as all those wine investment firms - is a direct consequence of Parker and co, and on the whole not positive.
I absolutely agree; whilst one's palate does expand its capacities over time, and whilst experience leads wine professionals to - on the whole - be able to predict what a young wine will do, I know that I myself cannot usefully taste more than about 100 wines in a day, and that refers to mature or light-tannin, low-acidity wine. At the Bordeaux Primeur tasting, on the other hand, when one is tasting barrel samples of very rich, tannic and acidic wines, one should bring that number down by an order of magnitude. I used to simply take a list of the 50 or so wines that meant the most, economically, to my company, (all the "big names", and a few we expected to be in any given year) and restrict myself to tasting perhaps 25 of them before lunch and 25 after. To see certain, highly respected persons in the wine world almost running down the tables, tasting everything at a rate of knots and dashing off one-line, or epithet, notes, later to be fleshed out into the "mocha, cigar box, leather etc etc" things that the public expect is a most disillusioning spectacle. Any detailed notes are produced after the fact, and are generally "generic Cheval Blanc" or "generic Cos d'Estournel" adjusted for vintage conditions and including whatever epithet they jotted down during the en primeur dash. People like Parker pretty much have to taste everything available at such tastings, which makes me even more skeptical of their opinions.