Sprite is making excuses. Their problem is that their parent company hasn't produced anything new since the original Aokana (as opposed to the follow-ups/FDs). Their other subsidiaries are completely dead, and FDs rarely sell as well as original material (exceptions exist, but they are just that... exceptions).
To be fair, there definitely is some contraction. Japan's economy isn't looking good (looking at yet another recession), and the otakus of my generation, the generation that mostly created the 'moege boom' (no, I didn't coin it, I translated it from a friend's sarcastic comment a few years back) by becoming obsessed with SOL have less money to play around with, as they start thinking about retirement. The generation below us (in Japan) is a lot less laser-focused on SOL (fantasy being the big thing right now), and as a result, more money is going into easily available (and cheap) webnovels and LNs. Nukige still retain their relevance (there will probably still be nukige until the fall of civilization or the generation of sex VR using neural links), but visual novels increasingly don't have the material the younger generations want for the rest of it. There will always be a 'core market' for SOL (because nostalgia for youth is an eternal theme), but it is definitely going to shrink.
The simple reality is that a lot of companies are already trying to adjust to the new reality by testing the waters in new genres (just look at Navel, for instance), but I really have no idea where things are going to go from here beyond a feeling that the current way of things isn't going to last a whole lot longer (relatively speaking, for someone approaching middle age).
Edit: Incidentally, this is just my opinion, based on what I've seen being put out over the last year and a half... the amount of VNs trying - usually in a really half-assed manner - to break out of the charage/moege mold have been increasing in proportion to the rest. There are still a hugely disproportionate number of SOL-focused games, but more and more it looks like the producers are trying to grab the attention of a different generation. My generation in Japan had a toxic level of SOL obsession, and now that they have less money to play with... SOL eroge just aren't as much of a priority. Of course, chuunige (my favorites) aren't in great shape, either (since chuunige companies are historically reliant on the sale of goods and long-term sales over initial game sales). However, in absolute terms, this is a much bigger blow to SOL (though in relative terms a bigger blow to my favorite genre).