Pretty enjoyable game, I really like it! here's my feedback for you:
1. hard to say which skill I enjoyed most, Stillmere was the most engaging, but Emberwood felt the most rewarding
2. Stillmere probably became the most repetitive for me first, but I think that's less to do with the gameplay itself, and more to do with the pacing. Speaking of...
3. I think the pacing honestly was way too fast for everything except Stillmere, which was the one skill lagging behind everything else for me. I'd unlocked most of the game before I'd really got a proper handle on what it was about, and at the end I didn't really bother finishing to level up Stillmere because it was getting kind of repetitive.
4. Most of the mechanics seemed pretty well integrated and self explanatory, I didn't need to read the instructions at any point to understand what to do.
5. With some improved pacing and a few more elements to it, I can definitely see myself playing a full game of this! It seems pretty well polished and has a lot of interesting elements to it.
Additional feedback that doesn't fit into the rest of the questions:
I really like the concept of the gear, but currently it feels a little half-baked. I honestly wasn't really paying attention to it for most of the game, and the constant pop ups at the bottom of the screen did start to get kind of annoying, especially for the gear I'd outclassed, so having an option for being able to turn that off would be nice. I think if there was some way for it to be integrated where using it felt more like an intentional choice than just an afterthought that it could work really well though.
This might just be a continuation of the pacing problem, but I feel like I breezed though the guardian fights far too quickly for me to even notice I was unlocking stuff until I went back to it after the fact. I actually really enjoyed the gameplay of those parts, but didn't really get to appreciate that because they didn't last very long.
The main difference between the pacing of Emberwood and Stonehollow vs Stillmere that I noticed was that for the first two, the levels were the bottleneck for the next unlock, whereas for Stillmere the bottleneck was gathering the materials, which led to it being a bit lopsided where I would have tons of materials for the first two but lower levels and really high levels for the other one but basically no materials. Just thought I would mention that if you wanted more specific pacing related feedback.
I think this game has a ton of potential! I'd love to see more mechanics introduced in future and a bit more depth to the gameplay (I think it would be fun if the different skills were a bit more integrated with each other than being wholly separate, but that's just one direction you could take it in to add a bit of depth). I look forward to seeing what you do with it and I hope my feedback was at least somewhat helpful lol