I suspect you have planted nothing but Class "A" plants..i.e. clematis that bear bloom on the old wood...and new bloom comes at the top of the vine--where it stopped growing the season before.

You should really experience plants that bloom on class B and class C --to which bloom on old .....and new...
and simply on new wood.

I made the mistake of planting 6 clematis ...on an extended trellis on my south wall of my garage....lots of sun there.
Unfortunately, I lost track of which ones were class C...and which ones were class B....thus when I got at the trimming, I know I cut back some plants that I should have just cleaned up...while others, I cut right to the ground.

I pay for it with loss of bloom...on some...and loss of lots on the others.

Only by remembering what I had done did I then take note of flower and began the slow process of re-learning what my plants are.

You cant harm a clematis by not trimming...or by trimming at the wrong time....only set back bloom.
It is though disappointing to have not pruned and then find out the blooms only come at the top of the plant...not anywhere else. That's what happens when you dont cut back one that only blooms where the new wood produces bloom....at the top.