Why would you remove ground under the switch node, exactly where it does the most good (reducing height of traces above ground, minimizing loop inductance)?
You also show only +3V3 under that area, which isn't connected to anything else at all, it's a dead end and no point to pour over the board. Board isn't big enough to provide capacitance value (it'll be what, 100pF if that?), nor would it be connected to anything where that would matter.
Plane capacitance is a factor in the 10MHz+ range, where local IC bypass dominates, and for which plane can substitute. This is all for naught behind even some inches of hookup wire (20s of nH)), and it looks unlikely you'd have such an intimate connection [as inner planes] from this board to another. (And, further assuming your load is one where such high-frequency bypassing matters; many don't.)
This would be materially improved, actually, if reduced to 2 layers -- pouring GND fully on bottom and nothing else.
Height above GND can be tweaked by choosing a thinner board, if you like (0.8-1mm, or even less really), but I doubt it matters here.
Tim