Any chance we can get some confirmation of the roadmap for old SP2010 workflows? SP2010 workflow is still present in the preview SPSE installation, but how long is this going to be around? It has already been deprecated from SPOnline what's the strategy for SPSE?
For customers with solutions based on old versions of things like Nintex or SPD workflows based on SP2010, they'll need to know when they're going to have to make the jump to something more current and deal with the redevelopment.
I don't think that we should compare SharePoint Server to SharePoint Online.
The retirement of the workflow engine in SPO was Microsoft trying to save on the bills and (probably) converting customers to use something which brings more money, the Power Platform.
On the other hand, there isn't really anything else available for SharePoint Server. We could say that the Power Platform can be integrated with SharePoint Server, but that would only be interesting to a small group of customers.
Plus, we have the backward compatibility requirement. It is quite impossible to retire a component which is being used by end users, this is the same thing why InfoPath is still part of SPSSE.