Hazmat gives Rad resist with no armor, power armor gives armor + rad resist.

And power armor players pay for that benefit by not getting legendary power armor. Power armor would be worthless if you could equip a full set of legendary basic armor underneath a Hazmat suit (which provides a ton more radiation resistance than power armor, in case you didn't know).

I feel the biggest argument for the hazmat suit is there is a large group of people that don't like power armor but want to do endgame, there should be SOME method for them to do nuke zones

If you build around it, you can absolutely run around in nuke zones with just a Hazmat suit. Even at like level 20 I was running around Whitesprings in just a Hazmat suit and tanking ghouls easily thanks to Blocker. If you add in armor perks like Ironclad or Barbarian as well as mutations like Scaly Skin and flat damage reduction from something like Blocker or Lone Wanderer, you can absolutely be fine in just a Hazmat suit.