First, the product was created for both the producer and the DJ as a bridge between the two worlds; DJs who want to add their own production / remixing into their sets, and producers who want to expand beyond the studio.
Is this product perfect? Nope. Browse through these and other forums and chat groups and you'll find plenty of complaints and wish-lists. But did the planning team do things right? Absolutely. They've created a brilliant product that comes in at a reasonable price point, and have, as you pointed out yourself, already included 3 major updates which included many additional features requested by users. Should those have been included at launch? Perhaps, but it could also be that they were on a deadline to manufacture and release the product, and as such weren't able to match on the software side to a degree they were satisfied with including at that point, thus updates.
As this is a unit for both the DJ and producer, they've omitted many advanced features that other hardware may include, such as CVs and gates; the sequencer is digital, and doesn't include those kind of advanced (and analog) features. Besides, if you're already into production and know what those things are/do, chances are you already own hardware capable of doing it and can figure out the best way to marry it all together with the SP-16 anyhow.
I agree that more can be done to market and promote the SP-16, but the Dave Smith name wasn't used simply to push this product into any limelight. He was an integral part of the planning and design of the filter module. Pioneer DJ wanted to make the SP-16 a unit that DJs and producers would love to use, and the Dave Smith analog filter was a great choice. With that relationship, the AS-1 was born - featuring a monophonic version of the analog synthesis engine in the legendary Prophet 6. This unit is designed to do what you're asking for re: the x0x units; synthesis. The SP-16 wasn't designed for it, so features like accent and slide aren't necessarily required on the SP-16 side end as they can be programmed into the sequence of the AS-1.
Rest assured, there are more updates coming and user feedback is certainly valuable in steering the direction of their efforts, but also note that much like the 32s memory limitation, there are other hardware limitations that will prevent certain features or functions from being included. It's unfortunate, but that's the reality with hardware.
Long/short: It's a great unit with a lot more to come via updates, and your feedback helps define its future.