You don't need the clutch to change gear, it only makes it easier. If you know how to change gear without using the clutch it will help you to diagnose what's wrong.

Any two gears to be engaged must either be stationary or rotating at the same speed. The synchromesh mechanism in the gearbox ensures this happens. All the clutch does is temporarily disconnect the drive to make gear changing smoother. But you can change gear quite easily by matching the speed of the driven gear to the speed of the driving gear, and when they are they will engage nice and easily. Older drivers may remember having to double declutch. This was because gearboxes years ago did not have synchromesh, and commercial vehicle gearboxes have only had full synchromesh for the past 40 years or so.

So if you cannot change gear at all without difficulty then the clutch may not be the problem. It's always easier to engage higher gears than lower ones. If you cannot select reverse without it crunching then the clutch is likely to be the problem.