Some work is not meant to be done quickly and not meant to be done by a specific date either.
It is not unreasonable to expect output and results in time to be able to progress, but slow work needs time.
Pin a deadline on or timebox an activity and be prepared to make trade offs.
Trade offs could mean less than ideal.
Perhaps “less than ideal” is what’s needed for the work to be done.
Also…
For an even longer (much longer) read, check out Driving engineers to an arbitrary date is a value destroying mistake from Gandalf Hudlow on iiSM.org