A fresh evolution on the SRW formula
If you've played any of the recent SRW games (V, X, T) then a lot of core mechanics will feel similar. But SRW 30 adds a fresh spin with an open-ended Scenario map, where's no real forced path for a playthrough. You get to pick which missions to play in which order, within certain 'chapter chunks.' The game will sometimes force you to deploy on a stage if you ignore it too long, but you have a large degree of freedom in what missions to play.
Added are 'Front' missions which are infinitely repeatable grinding missions, to help you hit the level and upgrade caps if you feel so inclined. The enemies in the story stages do scale to your level, so you'll never get overlevelled, although some of your less used pilots being under-leveled can be an issue if they get force deployed.
The DLC is new for SRW 30 in that in addition to adding optional missions with power parts, you actually have DLC units to recruit as well. While none of them feel 'game breaking' or 'pay to win', they definitely add fun new toys to your toolbox. I definitely recommend picking up the season pass if you want the DLCs.