Ah, a common trait within the art world - the existential angst of being an artist.
Biographies of many of the great (and not so great) artists reveals this problem in varying amounts, be they writers, painters, dancers or photographers.
From a very Buddhist perspective - everything changes. Our creative work will not only change but the appreciation of it by both ourselves and others will change. If you see the changing attitude to your work as natural progression, changing aesthetics, and the continual transformation of yourself as an artist, then re-evaluation of past work is normal and not to be feared. If all of our work was wonderful and perfect for eternity, then we would have nowhere else to go as an artist and we could spend our life gazing at our first roll of film in stunning appreciation of its perfection.
On a practical side, the suggestion of creating specific film/camera/subject projects is always a good one and it's worked for me when my pics start to look mundane and uninspired. In other words, change something and assume nothing. Dig out an old lens and only use it wide open, shoot pinholes, go monochrome, develop your own.... the list is as long as creativity allows. New kit can ignite creativity, but it's no guarantee...
Let me finish with another Buddhist quote:
"Every day the intelligent person learns something new, but the wise person gives up some certainty."
