I only load 9mm, 38/357, 38 Super, 41 Mag, 45 ACP and 45 Colt. And only about 15k per year.
I started reloading in the late 60's when the hot new thing was carbide sizing dies. I acquired Lyman carbide dies for the 38/357, 45 ACP, and 45 Colt which I reloaded at the time.
After about a forty year layoff I started again about four or five years ago. When I added the other calibers I bought the Lee four die sets. Then I replaced my Lymans with Lee four die sets.
I am not the best shot in the world and may be close to the worst. However, I have seen absolutely no ill effects from the FCD. All I load is lead, except for 9mm. If it squeezes the bullet down like some say it does not do it enough to have any practical effect on accuracy. Nor does it loosen the neck tension on any of the rounds. If it does, that means the user doesn't know how to adjust it.
If your cartridge is for a revolver the FCD does a roll crimp. If for a pistol it does a taper crimp. If you change bullets you don't have to start over, all you have to do is adjust the bullet seating die. The crimp die remains the same. As stated by others, the handgun FCD is a completely different creature than the rifle FCD.
If your FCD is squeezing down the cartridge it is because something else is wrong, not because of the FCD. In all likelihood if the FCD has to squeeze something down to SAAMI specs, the cartridge would not chamber anyway. This is what it is made for. A last step check.
Of course you don't have to use it, it just makes things easier. You could use a pipe wrench to adjust your dies, but a Crescent is easier. You can shift gears in your car, but an automatic is easier. And I don't feel like I have inferior intellect or sloppy habits because I use a FCD, a Crescent wrench, or an automatic transmission.