This "Definitive Edition" introduces some nice quality of life changes to what was already a very enjoyable game. I could do without the improved graphics, but it's hard to go back to the version where you can't zoom out as much or customize the UI and hotkeys. Overall, I would say this remake is a complete success in that front.
Other changes which don't affect gameplay have been made for the sake of authenticity, although some are just weird like changing "colonial age" to "commerce age". I'm unsure of what that accomplishes exactly.
I'm also not a fan of the name because "Definitive Edition" is normally reserved for the version that contains the full experience, but they have added more factions to the game as DLC after release. I don't think there's anything wrong with them making more content, far from it, but I would expect the people who don't want to put the word "colony" in their remake to be more careful with words.