Should we terraform Mars?

No. Mars is an inhospitable wasteland that will never be truly suited for humans due to the differences in size. Our planet is currently turning into a fucking wasteland and anyone who thinks that they can just create a new planet is delusional. Our planet is also still viable for many more billions of people if we could just take care of it! Things like permaculture are far more sustainable for larger populations. In a few hundred years, once Elon is long dead and forgotten, and if we can somehow be living in a form of a sustainable society, fine. (Also as far as terraforming planets go, if we were thinking about ever doing something like this we should be looking at venus, not earth. It's so similar to earth in terms of size that it's often called our sister planet. It also may have supported life sometime in the past.)

TL;DR: Hell no, for the next 500-1000 years and until our planet is livable.

It would be a huge project, taking centuries, with kind of limited returns. I would be probably not opposed to it if someone were to start such a thing, but I think orbital habitats are the better place for humans to settle in space.

I dont think it'll ever happen. Mars doesnt have a magnetosphere and as a result solar winds would erode away the added gasses and water vapor we manage to add into the system. Even if we were able to manage to get a breathable replenishing atmosphere I imagine the solar radiation would do bad things to us. We'd need like science fiction levels of shielding to keep it livable and we'd need to reach far off sci-fi levels of technology.

I imagine since there is an atmosphere that a pressurized dome city would be less fragile than say a structure on the moon since little holes and leaks wouldnt lead to dramatic explosive decompression. So colonization might be pretty doable but I think a green mars is unlikely.