You bring up good points and are generally correct. I haven't experienced a high end SR outside a music store and the high end ones didn't seem thin, but neither did my 300E until I brought it home. Thing sounds awesome until it's in a mix, then it's just gone.
Strings do make a big difference too. An SR really needs flats or, if you must nickle rounds but personally I don't like nickle as a string material. There's always something missing from the sound that cobalt and especially stainless steel bring whether flat or roundwound. Anyway strung with Chromes, with a fresh Duracell (another thing people forget when trying actives, use a good battery!), in P bass mode it would sound pretty damn good and would actually sit nicely in a mix.
At the same time it's why I'm trading it in tomorrow for a P; why copy the sound in a less comfortable (for me) bass when I can drop it and a few bucks for a bass I'll mod the hell out of and love right out of the box?
Which brings me to the active bass learning curve and mindset. Not only do you need a good battery but there needs to be an understanding of the difference between a bass, pedal, and amps EQ and how they interact and factor into the overall sound.
So yeah lots of people trying SRs with rounds, cheap and/or dying batteries, and no understanding of how the bass' EQ relates to the overall tone/signal chain will yield a lot of it sounded bland, flat, thin, and similar opinions.
All of this is what creates this weird polarization with Ibanez where as most people love em or hate em. It has less to do with the bass and more with the bassist. And that's just the cost of them being so versatile. That and set flat they will sound thin and bland, they're designed that way for a reason. The SR line is a make your own pasta. In flat you just have noodles, but as you change the EQ and choose your pickup and whatnot you're adding sauce and fixins.
A Fender P bass on the other hand is pasta ordered from a menu. You get a choice of how spicy it is but the sauce and fixins are already there.
Not to say either method is better, just different.