I think those control issues you mentioned with the 8 directions and no Dpad for 2D areas might just be a PC version issue, oddly enough, I think I've heard about that before. I just loaded up the free demo of the Switch version on my Switch and tested that and movement was not limited to 8 directions there, I had full directional control (albeit Sonic's movement was still stiff because this is Forces we're talking about, but it didn't have a limit on directions), and also the Dpad on the Pro Controller also registered just fine for movement in addition to the analog stick, 2D areas included. So it seems they just neglected controllers for the PC version of Forces for some bizarre reason.
I think those control issues you mentioned with the 8 directions and no Dpad for 2D areas might just be a PC version issue, oddly enough, I think I've heard about that before. I just loaded up the free demo of the Switch version on my Switch and tested that and movement was not limited to 8 directions there, I had full directional control (albeit Sonic's movement was still stiff because this is Forces we're talking about, but it didn't have a limit on directions), and also the Dpad on the Pro Controller also registered just fine for movement in addition to the analog stick, 2D areas included. So it seems they just neglected controllers for the PC version of Forces for some bizarre reason.