Older Boeings had a “binary” FLCH. Always full idle in the descent no matter the altitude to lose. So, if that’s the way your jet works, using it in the terminal area and/or for a 1000’ descent really doesn’t make much sense. If you were hand flying that descent you probably wouldn’t slap the levers back to idle either.

777F logic is a bit smarter now. I have to assume the same about the 787, 737-800 (or at least guppies newer than that) and new 767Fs we’re getting.

Maybe they’ve even gone back and updated some of the older models. But, old or new, FLCH doesn’t “always” do a gentle 1000 fpm descent as someone indicated. Use it going from FL300 to 10k at 320 indicated and see if you get anything close to 1000 fpm.

On the 777F, FLCH uses thrust as required to generate a v/s of 500 fpm for each 1000’ to climb or descend. Target is a 2 minute climb/descent. More than 2 minutes, it uses climb or idle thrust.

In a decent, thrust FMA goes to “hold” so you always have the option to bump up the power and reduce the descent rate if you think it’s going down too quickly.

All that said, V/S is a great tool in certain situations. Terminal area descents, light jet climbs in busy airspace with traffic above, foreign rules dictating specific rates as you approach target altitude, etc.