I hesitate to focus on a hurting stalemate, because that predisposes us to overlook the practical power of the high road.
I won't claim that the high road is powerful enough to dominate current events. Of course all the many distressing points made in the last x posts are correct. But there are a couple of practical reasons for Democrats to consider sticking to the high road anyway, meaning not to pack the Court if they get the chance.
I as a voter do track the moral consistency of parties. Mistakes happen often enough that I can't find any perfect party, but if Dems retaliate by Court packing, I feel they will have lost a slice of moral authority that they can retain by not Court packing. Some other voters pay attention too. The argument that Rs were inherently conflicting with their own stated principles by inducting Barrett now was quite clear. Even if it wasn't strong enough to switch a lot of votes, it counts for the future when new voters choose party allegiances and old voters occasionally switch or stop voting. Right now Dems are the aggrieved in this matter - they won't get tit for tat from Rs, but they may increase their voter share over time by maintaining that status as part of their ongoing identity. It gives them a chance to build a moral profile as a basis for future loyalty (more accurately, it prevents them from losing such loyalty). Why do a big brand damager when the likely outcome is just a continuing arms race?
Then there's the Limited Time problem. Even if they (we) had more than 50 Senators, court packing would be a big issue sucking up time and energy. No way even a Senate-controlling Democratic party can accomplish the bulk of its platform in one term. Since Court packing brings problems not just benefits, I think the balance of value is better on other issues, such as Covid19, climate progress, restoring international respect including functional alliances, economic stabilization, and so on. Biden is wise to have sidestepped Court packing.