Is there any point to having a power plane for a single device?
I've done a half dozen simple but moderately high frequency (50-100 MHz) opamps on two layer boards with no dedicated power planes and never had a serious problem that a power plane would have fixed. Provided you route the power lines carefully, that you keep as solid as possible a ground under the power and signal traces and the board is simple enough you can make it work.
I think it usually isn't done because four layer boards are only a little more expensive but are easier to work with and much more versatile, especially if you want to have more than just an opamp.