Welcome back to Paragon City and the Rogue Isles!
If you play blue side, a lot of the early leveling experience has changed. Galaxy City was sadly destroyed by a Shivan meteor in Issue 21. Atlas Park is the one and only blue side starting zone now, unfortunately. With the destruction of Galaxy City came a revamp of the blue side lowbie experience. Because there were so many people leveling blue side lowbie alts over and over and over again over the years, people got tired of the same old thing. So now there are multiple ways to level blue side. You have the Shining Stars story arcs with Twinshot, followed by Shauna Stockwell in Kings Row, then you can do the Faultine mission arcs (which I strongly recommend). Or you can do it the old school way with the Hollows, etc. It's up to you.
Like Ukase said, there was a new system added around Issue 13, called the Ouroboros Flashback system. It allows you to "flashback" and play low level story arcs via in-game time travel. It essentially acts like your own task force, where you can play the vast majority of the game's story arcs. So you can certainly pause XP like you've been doing, or continue to level and then go back and experience the story arcs by "flashing back" to them via Ouroboros.