It's an ambitious choice to try and role reverse not one but two games, as well as take on a 3D game during a game jam. I think for the most part, the idea works. People have already mentioned the text tutorial and overall game pace, but the fact that we can kind of figure out the gameplay despite so does demonstrate the idea's potential.
I do find the environment and sprites very well done, but I'm not a fan of how the sprites look alongside the smooth, more modern 2D UI. The sprites look more at home on the 3D map than it does there. I mentioned Octopath Traveller in DMs, but that's a good reference for UI that might work with the sprites. A flat black translucent rectangle might look more cohesive than bright orange, and you wouldn't have had to create any more assets either.
For the tower defense portion, feedback on units attacking towers would greatly help the game feel. Likewise with the shop, a little "dingling" chime when customers enter the shop would also help immensely. Never underestimate the importance of audio in a game, even if it's not one of the elements you see on the front page.
What this game is is ambitious, and for a 48 hour game jam, it might have helped to scope down in either the art (you can't cheat the environment in 3D) or the gameplay (for time to make a tutorial) to achieve something that's more polished. That said, the fact that your team has accomplished what it has in a surprisingly stable state is a testament to your abilities. Good job!