My Gibson B-15N features both those abominations (plastic bridge, adjustable saddle) and it sounds
great.
Yup, absolutely. I've had three vintage Gibsons with the plastic bridge & adjustable saddle (still own one), and they've all had a very satisfying tone. I also currently have 2005 Epi Texan ('64 McCartney reissue) with the rosewood bridge & adjustable saddle setup - and it produces a similarly great tone.
These bridges come in for gobs of hate, and often from luthiers because of their overall weight & because they're so far removed from what one would consider to be an ideal guitar construction method. Also, you have folks who may have played a Gibson with this setup & it sounded like a dog - but in those cases I'd bet the guitar would've sounded like a dog with a standard bridge because it was not a good piece to begin with. Finally, you have people who just like to pile on & have no serious experience with these bridges.
Note > The only one to totally avoid is the NON-adjustable plastic bridge, because string vibrations must travel from the saddle, through the plastic, and then to the spruce top. Here's the scoop on the adjustable saddle setup:
With the adjustable saddle & plastic bridge, string vibrations travel from the ceramic (or sometimes rosewood) saddle to a metal structure that is essentially similar to an archtop guitar's adjustable bridge. The metal structure is directly coupled to the spruce top. The plastic bridge portion is basically a hollow shell that ends up serving only one function > To hold the bridge pins.
As stupid of an idea as it originally was, what ended up happening along the way was that the adjustable saddle structure produced a unique metallic overtone that has appealed to many players over the years (myself included). Yes, some of these bridges have not held up over time, but neither do all standard type bridges. If the adjustable saddle setup has remained structurally stable over time, it's always worth trying one of these instruments to see if the tone produced appeals to you. The plastic bridge & adjustable saddle on my '66 Epiphone Cortez (Gibson B-25 clone) is completely stock & remains totally stable after 54 years.
To out-of-hand dismiss an instrument with this setup is simply a missed opportunity.