When I make my barre chords shaped like F (is there a name for those?), my index finger is sightly crooked so it doesn't press on the strings that arent needed (those that are pressed by the 2nd, 3rd and 4th finger) to make them easier to play.

I've been told it was a bad habit by someone who didn't explain me why.

Is it really that bad?

Thanks ^^
According to what you asked, its just a normal F major chord which contain F, A, C notes within the chord.

It's not really that bad to play something easier, but you will miss a note of that particular chord which can be a bass note or high note as an index finger usually press two notes in a row for a barre chord that give a particular sound to that chord even there's already the same notes on other strings but they sound different in term of an octave. Therefore, I would strongly recommend you to practice the barre chords and buy a chord book that contain shapes and notes within the chords where you would be able to gain the knowledge of chords a lot.
its not a bad habit because it concentrates pressure on those strings that need the barre making them clearer sounding. However you need to practice fingering Fmin and F7(or any min/dom7 chords) to get used to switching where you focus the pressure from the barre or youll end up playing a Fm and the third string wont sound.

Theyre called E-shape barre chords btw (or sometimes 6th string barre chords)