A lot of people are against an abundance of units like in TA I feel. Each unit must have a unique role so any duplication is viewed as superfluous and negative. But I am with you . As long as it is still balanced there is nothing wrong with some forms of close-to-duplication. If you don't like them don't build them. I like the visual difference on the battlefield of all these different types of units. One game I might build unit A, the next build unit A2 just for a difference, to mix things up.
I think many people are competition focused so don't like it. It obviously costs resources so the developers probably won't do it either. It is the sort of thing the community can make with mods so that is where I would look for it in the future. I think a lot of DLC are planned for the game (lots of new units to keep us happy? )and some companies who have that business model don't like unit mods as then people might not buy the DLC. I don't agree it has to be like that though, for a bunch of reasons i won't go into here.