I am not by any means an authority on anything Vintage, but am a student of the game of magic and the Vintage meta. I have not played magic in paper or online since the Waterbury. While some considerations in my life may be factors, there is another issue at play. Reading the content on the Mana Drain, I tried to think critically about why that is the case. Here are my 2 cents:
The format seems to have consolidated around two decks, with Mentor pushing out other blue strategies as the best win condition and Shops being a natural predator, but playing fewer lock pieces than ever. Some of this could be traced back to the restriction of Chalice (which allowed for 1-drops to become more worth running en masse, which may have contributed to blue preying on itself in the form of Mental Misstep, though Mentor really brought that to the fore) and LSG (making Shop decks want to close faster) and even the printing of Dack.
However, I want to focus on those restrictions from another vantage point. There has been more outcry from the community and more discussion about potential or actual restrictions in Vintage than in my past memory of the format (circa 2009, maybe). Additional attention from the VSL and MODO may be contributing factors to this, and many have claimed that the format evolves and stagnates faster than before due to Magic Online. The recent swath of B&R changes have not have the desired effect generally: Chalice and LSG restrictions made Shops perform better, Gush did not (yet) reduce the prevalence of Spheres, etc. Managing the B&R list is surely difficult, and there have surely been missteps recently (from where I stand).
For me, though, this is not the factor that has pushed me out of the game recently. Rather, I think it is the flurry of B&R activity in the form of restrictions that makes me less likely to want to play. Wizards wants to sell a product and wants to make the format as healthy and fun as possible; good on them. However, if the format will constantly be changing through (mismanaged) restrictions, I have less incentive to play. As @Smmenen mentioned in his post here (http://www.themanadrain.com/topic/1360/turbo-xerox-and-monastery-mentor/113), time is important. This is a contributing factor to people's stated beliefs that if you want to win, you should play Mentor or Shops and how that portends seeing those decks at the top tables.
I have no problem with either deck, or any deck really. I personally think that Mentor is too efficient of a win condition and the Chalice restriction made decks full of one-drops (or effective one drops; i.e. TX) too homogenized. Wizards decision to give B&R updates more frequently isn't a problem on its own, but making changes that frequently is. As there is no certainty that any deck that rises to the top won't have its legs cut out from under it by B&R policy, there will be less investment and less innovation, at least among a proportion of the player base.