Galaxy city is basically a very good tutorial, has a easy boss fight, interesting storyline with lore(and feels like you are a hero on a mission, and not doing random activities... For the first few episodes at least), and basically the quests aren't hard(even if they are. Unlike preatorian earth you have people to play with)
Only the following is needed for a complete tutorial-
Leveling up(outside of galaxy city)-Can be done with a quest/mission when you are expected to level up(The objective could be just talk to liberty girl, so as not to soft lock a player for leveling to 50 before doing main quest-line.)
The hospital system(could be they tell you they will revive you at a medical cart after giving you a patch if you fall in battle)
Enemy difficulty(Could tell you enemies before you enter as well)
And exit dungeons(can be basically a exit button you are required to press before you can evac to the main park)
Otherwise this is a very good introduction for new players. Especially if you prefer a officer or citizen that somehow got superpowers from the incident or has special training and had to save the world, instead of a generic superhero.
Plus it is underrated as it has cool lore
(it also isn't hard to be a hero or villain, as only one choice dictates the hero or villain, and it tells you which is which.)
It is also a very good story, like my man Matthaw Habashy>Than your Director/Main Guide(On hero side I mean)
(also if it is for the diffuculty compared to regular story, can be a simple nerf of enemies, it is mean't as a tutorial, even with alternative quest-line)