This is a tileset made by someone I'd guess hadn't read your tutorials. Which is crazy. My edit that follows isn't good, and i gave up because my neck aches and too much pixelling annoys. You use 38 colors for a tileset that doesn't need more that 24, and there's colors that are only used in 3-4 pixels on some tiles, various nears, generally a quite sloppy palette. There's a stamp in the middle of the trees, which is very odd. You use super-saturation to make up for some faults but in the end the tileset looks as if it's made out of candy and plastic. The lack of a cohesive palette separates each element of your tilemap into a separate entity. It looks as if grassland is swiming on an ocean of dirt, there's priority reading errors. Water is usually not opaque, therefore the color of the earth shows in the shallows. You need at least 3-4 different basic ground tiles to mix them so as it doesn't look like tilegrid, as your tutorial said. Darkest spots usually should be less saturated, not more, though there are exceptions. Do bushes need selout? Are they moving, so the selout theory comes into play where they couldn't read against a non-color-correct background? They're just sitting there. The bushes are too close to their tile limits, a bit square-ish.
When one works for a video game company, he gets used to working fast, efficient and with the tools that he needs, but here you're neglecting basics of pixel art, like a controlled palette and color reusing, and it ends up hurting your piece in a big way.
My edit isn't good, I'm tired. But I hope it helps a bit.
