In the first place, the mass of pictures currently being made is utterly daunting. You cannot stand out, it seems that every picture has been taken, my pictures look like everyone else's pictures. Mere technical excellence is clearly not enough, there are millions of people who are that excellent. Artistic excellence is not enough, there are many genuinely talented artists out there. Even a strong artistic vision isn't enough, there will be 100s of people with a vision indistinguishable from yours and a million pictures that look, whether by accident or design, like yours.
In the second place, the internet and sharing culture mean that anything genuinely new I produce, if it's interesting to anyone, will be picked up and copied and modified and evolved into yet a new thing all in the blink of an eye.
This is surely true, and surely depressing. I experience these problems myself, and I suspect you, Gentle Reader, do as well.
Let's back up and consider our relationship to photographs a bit. In the 1970s when Susan Sontag was writing about this, she spent a certain amount of time mulling over, roughly, the idea that a photograph was a moment in time, frozen, and made permanent. We treated photographs as permanent, eternal, records of a split second of time, and our relationship with them was built around that idea. This was true from the beginning of photography until sometime in the early 2000s.
At that point, things started to change. The model for pictures was no longer to place them in a shoebox or an album, where they would live on forever. The model for pictures was to share them digitally, usually in a most-recent-first arrangement. This meant a shift in how we view photos, we now treat them as ephemeral. They're a record of a moment in time which we share with others who were not there, which we save away and remember, but which will in a few weeks be too many clicks away to ever see again. We treat photos as ephemeral and impermanent now. At least to a substantial degree.
So it goes with the digital photographer/artist. The aspiring artist places his or her best work up, and then it gradually disappears into the past, covered up by newer, better, different work. We spend no time living with our work, or with anyone else's work. Indeed, the amount of time we spend taking pictures, and fussing with them, and fiddling and painting on them may be greater than the time we spend looking at pictures. Picture taking is almost a write-only process now -- we create them, we don't look at them. There's no time!
If you're frustrated and stymied by the overwhelming glut of pictures, of people "better" than you, of new processes, looks, software, cameras, and ideas, here's my advice to you:
Just don't take part. Do something different. Why fling digital copies of your work into a maelstrom of a billion others just like it? Make prints, or put your work in digital photo frames, do something else. Just opt out. If you care about your work, why would you relate to it as a piece of ephemera?
Sure, there are people that do what you want to do better than you. There always have been people who were better than you. Sure there are new ideas and new techniques all the time. Who cares? What do you want to do?
This doesn't meant to get off of flickr, unplug from the internet. It simply means that you should recognize that what they're doing hasn't got anything to do with what you're doing. They're experiencing one relationship with photos, one in which photos are ephemeral scraps of time, soon lost under new strata of new photos. Your relation with photos doesn't have to be that. Make prints, put them on your walls, enjoy the pre-2000 relationship with photos. Or, make your own relationship with them, invent something new that pleases you.
This also doesn't mean to ignore what other artists are doing. It means only that you should recognize that they are doing their thing, and you are doing yours. Steal ideas as they suit you, but don't feel any obligation to copy, to emulate, to follow.