To add to that:
Having a low mass slide means you will be required to have a very heavy recoil/return spring. I saw this several times 20 or so years ago when titanium 1911 slides were considered the next "big badA$$" thing...in order to have enough return force to reliably strip a fresh cartridge out of the mag, the low mass slide had to be slammed forward HARD. Serious detriment to accuracy (caused severe muzzle dip), really hard to work the slide under the best of circumstances...under stress with wet/bloody hands? Not gonna happen.
This has been tried, you know: rotary barrel (see Beretta Cougar, Grand Power K100, and Glock 47, for example...none terribly successful), a toggle bolt (see the Luger--great pistol, famously unreliable) or perhaps gas retarded blowback (see the HK P7--incredible pistol, but not cost efficient enough for even HK to keep making).
It just brings us back to TANSTAAFL.