You certainly chose one ambitious genre for this game jam. And while I think there are improvements that could be made, the fact you got a working RTS game like this working at all is impressive.
First I want to talk about the visuals. I really like the little intro with the text. It's simple, clean, and gives the game some proper set up. As for the game itself, the models don't fit great with the environment, but at I can tell each of them apart so that's good enough. I think it would have been cool if you really leaned into the simulation look with the game and made the environment just colored boxes and stuff, that way the other models would have all fit in the game better, or maybe you could have used some kind of prototype materials with the terrain system.
Next I want to talk about the audio.
Next I want to talk about the gameplay. You have all the necessary things to create the "starcraft" style base building and unit management, but the fight itself feels lacking. Basically, you made a really cool system, but didn't give the proper sandbox for people to enjoy it. I think the thing attacking your base should have ramped up over time, sending stronger units later into the game (if it already does, make it ramp more, eventually sending tanks). Also I think the units attacking your base should come in less frequent but more deadly groups instead of a constant stream. This would give a more realistic "attack" feeling, the way an actual player would attack. In addition, the little outposts should probably increase in difficulty as you get closer to the enemy base. Currently its hard to push through the first few outposts, but then really easy at the back once you have built up an army.
In addition, there were quite a few quality of life changes that would have helped. For example, I think you should always have most of your controls visible in game. I know they are on the itch page and they aren't super complicated, but I strongly suggest you don't rely on that. If you don't have time for a proper tutorial, I would say even throwing them on the bottom of the screen as a static UI element is better than nothing.
Also, I think there's a lot of ways you could have given the player better feedback as to what is happening. Such as "+xx" coming out of mines when you get resources, circles around selected units, death effects on units, particles, sound effects, and other small things I can't think of at the moment.
Overall, this game is certainly the most impressive project I have seen from you when it comes to programming, although it lacks some of the charm your projects usually have. I'm glad to see you tried something new though, and I can't wait to see what you make next. I apologize if this review was a bit much, but I'm doing this to all the games from this jam as I think critiques help us grow.