I'm not a huge fan, but some of my guitarist pals love it, and a few still use them for demos.
I guess it's more than the quality of the sounds, I think it's just that it doesn't feel like a synthesist's drum machine and I guess it won't be too popular on this forum. The drums lack variety (tho 233 presets at the time made it a market leader) but some of the samples are a bit lush becasue they've been sampled with effects, something that most synthesists would want to do themselves.
I think people also get a bit sniffy about the intro/fill-in features which seem a little casiotone like. Strange that the TR808 has a similar feature, but isn't criticed on the same terms.
One thing I remember about the SR16 is the sample and hold feature, which isn't really a synthesis feature at all, but the ability to set up 4 drum sounds to cycle for each time a pad is hit. Could be fun, but you couldn't pick what those 4 sounds would be, so actually it's kind of pointless.
I think when Boss caught up and released the DR660 which had a better soundset, then a lot of potential buyers probably viewed that as the better budget instrument.
Also around at the time were the R8, which was admired for its deep rhythmic possibilities, and the RY30, which was a pretty good percussion synth as well as drum machine. I think the SR16 was viewed (in my opinion fairly) as a class below and that reputation has kinda stuck. Still, tell that to guitarists...