I mean back in mk9 or mk vs dc I didn't hear peep about people making a case for Nitara, li mai, or Havik in those games because they were terrible.
I'm not gonna defend matteo for... well... obvious reasons...
However, just because the 3D era games were bad doesn't mean there weren't people who didn't like any of the characters... that was a lot of negatives, but my point is, I too like a good handful of those characters and would love to see them return in a modern MK, getting a redesign both aesthetically and gameplay-wise.
And I know NRS can do this if they wanted to, as they have definitely proven they can take even the most basic and soulless of characters from a past game and turn them into an interesting and cool character in a modern MK. I'm of course talking about Tremor here. Not to mention they took Nightwolf and Stryker, two of the most hated characters in the Trilogy era, and made them cool and fun in MK9!
Also, considering MKvsDCU was focused on MK1/2 characters, and MK9 was all about the 3 first games, it kinda makes sense that not a lot of people tried to make the case of bringing 3D era characters into those games. Because that's not what those games were about.
However, from MKX and forward there's great potential to bring some of those characters back into the modern era. I know that the majority cling on to the legacy characters, but there should still be room for other fan favourites.
Lastly...
Which is why I question you because you want them in for nostalgic reasons.
This is pretty much why a lot of people cling on to the legacy characters as well.