You may have noticed that not all TS restaurants at WDW are the same. Each TS restaurant has a different operating environment and important operating factors such as overhead and capacity vary greatly between them. Also people seem to think that all dining venues at WDW operate as a collective, the poorer performing ones are "bailed" out by the better ones. It doesn't work that way. Each venue operates as a standalone and has to deliver results on it's own.
But lets look at a couple of examples of restaurants which have not opened back up and perhaps why.
Jiko - Popular, upscale, high overhead, low capacity, and in a mostly closed resort. Already a low capacity venue with high overhead, limiting capacity further makes profitability difficult. Add to the fact that most of the resort is closed, this may create operational issues due to lack of staffing. (Applies also to Flying Fish, Yachtsman, Toledo - even though CSR is open)
Boma - Popular, high capacity, high overhead, and in a mostly closed resort. Would have to transition to a family style model which may not be workable, high capacity with low margin and high overhead requires max capacity, limiting capacity makes profitability difficult. Also as with before, the resort is closed which creates other problems. (Artist Point sort similar conditions)
Takumi-Tei - Very low capacity, very upscale, very high overhead, park restaurant. Pretty self explanatory cutting capacity of an already very low capacity restaurant makes it unworkable to open. Same things apply for Monsieur Paul as well.
'Ohana - Very Popular, high capacity, closed resort - If the Poly wasn't under construction this one may have been able to reopen, No monorail and limited parking are the reason for this one.
