It is nothing new that the RTS genre has been in decline and stagnant for several years now. They are mostly recycling the same ideas over and over. I remember that I played Earth 2150 a lot back in the days and it is the only RTS game i felt that really brought something new to the table.
In short, in earth 2150 you don’t have “build-in” units like in other games, instead the units are modular. That is, you research different parts, chasis and weapons and then using a unit editor to create your units, like lego. This was super fun to play with and yet I have seen not a single RTS game that tried to revive this formula over the years and innovate with it.
I think that with the current tech it is possible to use the formula of earth 2150 and make a really innovative and fresh RTS game.
That was indeed a great gameplay mechanic! Not super efficient timewise for the players like all over-detailed modular systems in games. But addictive as F… In RTS, it revolves more about balance and speed I think, so the idea didn’t trend. In 4X games on the other hand, there are other games like that. Galactic Civilizations II like SDirickson above said, and other I can’t pinpoint in my head right now. Maybe Stellaris? My memory is numb, someone correct me please.
On another note, I think “create your own” unit/ship/weapon/spell is a great concept. I gives a sense of freedom and achievement amazing. I remember combining the different elements of Magicka to find all the possible spells and the most powerful ones was such a blast!