The gameplay aspect, what I believe is often called "skinner box"
That's exactly right, that's what it is.
What drew me to play it was a video of someone fighting De Ragan on PSPo.
I always wondered how much of the (relative) lack of popularity of this game was due to inadequate marketing. Not that it sold very poorly, but perhaps SEGA could've increased its popularity and longevity simply by presenting the good parts of the game better. The big monster fights as you mention, and some of the cooler looking weapons in action, for example.
SEGA is known for their poor marketing and business decisions in the past, that was largely why their earlier systems crapped out so fast compared to their competitors.
Bad marketing, lack of good franchises and bad timing on their console releases.
Or they could've made the game last longer by upholding stricter rules regarding cheating. I haven't played on the US servers, but I always saw how people mentioned they were rife with cheaters. Compare that to the JP servers, where they had a very strong anti-cheating policy.
And they could've held more online events with special missions and bonuses.
For example, the JP version had these special missions where you would get collectibles if you completed them, and you could trade those in for equipment and cosmetics exclusive to that event.
And it also had a global counter of some sort like in MMORPGs, if players across the server killed enough monsters (or did enough damage, I don't remember), that would unlock special rewards too.
Those missions were generally very fun since they were new and they had boosted drop rates and/or experience, and they gave you several specific goals to work toward, which was a great incentive for people to play more.
I assume those kind of events were never held in the US version, since SEGA is also known to be stingy with those type of things.
That's the kind of thing that makes your game last, and I felt they could've made more and/or better use of that. You can't even say that it's a waste of money for them, because they also sold all these cosmetic outfits on PSN for money, so more people playing means more people buying too. And naturally, if many people are already playing, others want to see what all the hype is about, and start playing too.
So it's a virtuous circle that reinforces itself.
That's why I thought,
"if SEGA just made made their choices a little bit better..."
I often wonder how much of PSP2(/i)'s development Alfa System should be credited for ... and that Sega only acted as a publisher.
I read the same thing, so you're probably right. These guys know what they're doing.