Barre chords are tricky at first.

You are right that you only need a little bit of pressure.  And beginners often try to squeeze too hard.  But the trick is that you have to find the exact right placement for your index finger in order to barre the entire fret & cover all the strings.  You might have to shift your fingers around a little bit.  I call this microplacement.

Put your index finger as close to the fret as possible.  Make sure that the E, G, B & E strings are ringing.  You might have to wiggle your finger up, down or over a bit in order to make sure the strings are all fretted.  Sometime the divots where your finger is jointed might line up with a string & miss it!  So be very careful about making sure you are making solid contact with all the strings.

Then place the rest of your fingers one at a time doing the same thing.  Listen & look for problem areas.

When you find the location for your fingers where all the strings are ringing clearly, then experiment with how much pressure you need to apply.  Start to back off a bit until you find that spot of just enough to make the strings ring.

These tutorials cover barre chords for beginners.

https://www.guitartricks.com/tutorial/450

https://www.guitartricks.com/tutorial/464

Hope that helps!