I like the style. I agree that some transition between colors might help, but another option would be to keep the colors of the mountains and forests a little closer/more within the icons themselves. Not sure if you have a specific style (or a couple styles) you'd like to try and emulate, at least to figure out what you like and what not? But the way you've done this map, I'm actually kind of reminded of those hand drawn maps that have been "painted" in a sort of water color style. Even if you kept the brighter/more opaque colors, it would still look good.
Another thing is that your icons look smoothly painted, almost vector-like, but the 'paint-outside-the-edges' look of the mountains and forests doesn't quite seem to "match". Your font works beautifully, though, although I do agree the frequent use of curved text does make it hard to pinpoint which feature a label belongs to.
One final thought on style - the forest and mountain lineart is colored a darker color of the paint color, but the coast line and 'waves' around the coast are black. Maybe change the coastal lines and waves to a dark blue?

Overall, though, I like what you have here. Definitely looks like you've got a lot of potential, with this map and future ones! Good luck ^-^