I love terraforming in games. I have since I played MOO2 and Stars! I'm currently dragging my feet on starting new StarSector playthroughs while I wait for updated terraforming mods.
Gameplay-wise I prefer terraforming that doesn't focus on everything aspiring to perfect Gaia worlds so much as terraforming that shapes and reflects being perfect to the industries that the location specializes in. Water worlds are amazing for bio industries, asteroid belts are great for mining, and lagrange points (or stable locations) might be perfect for something like shipyards or research.
I like how vanilla boosts colonies with rare items. I like the idea of colonies being barely a blip while terraforming is ongoing- crashing a water comet into a planet sounds like something detrimental to pre-existing infrastructure. I like terraforming being a long term investment, and I like the idea of factions wanting to buy or steal that investment.
I prefer more interactivity with terraforming to less. I like consequences to choices (can a colony assert it's independence or adopt a faction? what happened to that decivilized population?).
Basically terraforming in games is my jam. I totally get it if there's a desire to focus on practical 'quality of life' changes to various playstyles. I just wanted to throw in there that you have my full throated support if you want to make terraforming itself the playstyle
Cheers,