For the kind of mountains and hills that they are, they seem fine to me. Of course, there's always more you can do, and different techniques you can use. Sometimes, on some maps, you finish a terrain feature and move on. Maybe you move on because it's too much work to keep messing around with it. Maybe you move on because you've reached, for the moment, your level of skill and need some more personal development time before you'll be able to make something better. I think we've all been there.

If you were going to do more to the mountains, you could...
1) Give them sharper, more intense shadows and highlights. Especially at the tops...the shadow and highlight should both be most intense near the peak, which doesn't really seem to be the case for most of your mtns here.
or
2) Make them blend into the terrain more, with little contour lines or with patches of shadow and highlight that blend the bases of the mountains into the surrounding terrain.
or
3) Do the "connected mountain ranges" thing. You don't have to go nuts and connect them all...you could pick some peaks here and there and draw the connecting ridges in between. There are lots of decent tutorials for how to do this in many places. I just recently posted a bunch of mountain drawing tutorials over in that forum.
or
4) Pick some tall peaks to put some snow caps on
or
5) Weave your rivers into your mountains to a much greater degree, winding the streams around the bases of the peaks and creating that "embrace" between the flowing water and the elevated land it flows from

Or any combination of the above...