100% agreed. The pace lags and it's hard to stay motivated at the current rate of progression. I think definitely making X2 more plentiful and cheaper and perhaps even X4 makes sense to keep the income per second more progressive.
This also would give it more of the classic progression feel of doubling or quadrupling income at level milestones like 10, 25, 50, etc...
You've done a great job on the game. I've thoroughly enjoyed playing it (Im an idler and have played them all starting from Cookie Clicker way back).
Do you plan on having more Rebirth upgrades or anything else in the future or do you feel like the game is pretty much complete at this point?