Did we? Where are those fusion plants installed?
> Not compared to Nuclear, Fossil Fuel, or PV R&D + subsidies
You are probably referring to this document: https://www.eia.gov/analysis/requests/subsidy/pdf/subsidy.pd... . A huge share of the $183.3 billion are tax expenditures, which is to say they reduce taxes on activities related with energy (e.g. nuclear decommissioning is tax free). That is not the same as throwing money at those technologies R&D, but it counts as subsides because they can operate more cheaply. Only $11 billion of the $183.3 is true expending. But they mix R&D with other direct expending, like guaranteed loans. In Figure 11 we can see that R&D for all renewable energies is less than $300 million.
Fusion energy don't want tax expenditures, they want cash and lots of it.