Like everything, it's not for everyone. I love the new series but personally prefer the classic series. I don't know anyone who likes the new series but dislikes the old which I think says a lot
I remember back to the dim and distant times. Simpler times when the Doctor only had 12 regenerations and the Face of Boe actually still looked like Ianto (don't believe the misdirection at the end of LOTL). I started to watch the show which, at that time, had Tom Baker in it and become utterly obsessed, getting my Dr Who annual and taping the soundtrack off the telly so I could listen to it later. I then saw a Jon Pertwee story and couldn't believe my eyes! What the f*** was Worzel Gummidge doing in my TARDIS? Who was that lovely blonde with a squeaky voice. Why was the music all harsh and metally? WHAT HAVE THEY DONE!!! I can only imagine the culture shock for someone who has only seen the 2005 incarnation onwards - it is virtually unrecognisable.
Yet for some reason, and one which is down to the genius of both iterations of the series, the soul of the show remains intact. Watch a show like Robots of Death or Earthshock and the same themes and issues crop up. Classic Who, I think, requires the viewer to engage a lot more and put a lot more of the pieces together. It requires us to ignore a lot of the obvious deficiencies and engage more closely with the story and perversely I think this helps us as viewers. Don't get me wrong, the 21st Century production values are amazing and the show is a wonderful, visual treat. But the Classic Series has an intangible charm and an ineffable quality that still survives.
I will say, one of my best friends completely disagrees with this thesis, calling it 'pretentious, psuedo-intellectual drivel'. He thinks the new show is 850 times better than the old one and whenever i venture a contrary opinion he reinforces his argument by singing 'Wobbly Sets, Wobbly Sets, Wobbly Wobbly Sets' to the tune of Rhubarb and Custard (the cartoon narrated by Richard Briers).
He may have a point.