I have the same feeling. And it's not because "Man, there's just so many less options in Starfinder!" My group pretty much only played out of the core book and APG for all of Pathfinder, the Starfinder Core book gives you at least the options of those 2 books. At least it LOOKS like it does.
That's the problem in my view. Starfinder is a game that LOOKS like it has a lot of choice at first glance, but once you look at it closer and take into account the small rules tweaks you realize there is actually very little choice. The options of things you could do with the Feats or Actions just aren't there, because so many of them conflict now. Let's say you used to be able to trigger 3 Feat abilities in one attack round, most likely all three of those abilities are now an exclusive attack. You can only ever do one of them. And if you can only ever do one of these 3 options at a time, the 2 that are less commonly useful will probably never be used. And if they won't be used, why take them? They are really just window dressing.
That's why it feels like the 'plate is too small'. Because even if you have a big plate, you're only ever going to use a small part of it.