Usually, hydraulic problems in the clutch are internal seal leaks, and can be diagnosed in this way:
1) Make sure the fluid level is ok (perhaps obvious, but...)
2) Engine running, depress clutch, shift into gear.
3) Keep clutch depressed for several minutes (let's say, 3 min)
4) Did the clutch start to engage in this time? If not. slowly let out clutch, and see if it starts to engage unusually early in its travel.
Failing that test is a good indicator of a partial failure in hydraulicsville.
Throw out bearing?:
Does a new noise start when the clutch is depressed, snd stop when it is let out?
The clutch will not fully disengage if the T/O bearing is starting to bind.
How long has it been?
This can have miraculous results if the oil is really dirty.
On an Audi I used to have, I found that the prior owner had used a thick gear oil in the transmission by mistake, when it called for a motor oil viscosity. The symptoms were similar to yours.
Shifting improved markedly.
Just a few things to try before condemning your transmission...
1986 300E 5-Speed 240k mi.