However, in the far future, might it not be possible to "create" a creature that is dinosaur-like in appearance? Technically all living things consist of the same molecules at a genetic level. That's very far-future stretching-it sci fi, but what would be the barriers to that, beyond technology?
I suppose it would be entirely possible to one day be able to "turn on and off" certain genes to create an animal that appears dinosaur like. This would probably best be accomplished with birds who are a more direct decedent of dinosaurs than anything else on earth.
However in this case, we are not really creating a dinosaur, just a new species of animal that has some dinosaur like characteristics.
What would the barriers be? Many.
It would require the ability to completely map and control an animals genome. We can map genes and genomes very accurately now, the control is the problem. Its not as simple as "turning them on and off". Some genes require multiple regulators to work, some genes work on feed back systems, some genes regulators are down stream of the gene or on a different chromosome. It gets complicated real fast.
In my opinion (and despite what the sci-fi writers say), we are a long, long way off from movies like Gattaca. Though it is nice to imagine sometimes