When will we see stand alone stories again?
Jesus Christ, you can be melodramatic sometimes. Destiny changed everything; of course there would be aftermath stories. Despite that, out of the six follow-up novels so far, fully half of them have been completely standalone (Unworthy and the two Titan novels), and several reviews have stated that you can read all the rest - ASD or LTP or Full Circle - on their own and enjoy them just fine.
And the forthcoming four Typhon Pact books?
...ARE ALL STANDALONE STORIES TOO.
And even if that's not good enough, all the 24th century books - and in fact, all the books *PERIOD* next year - are standalones (in your sense of not being part of crossovers; a couple are part of ongoing series, but you don't seem to have any problem with that).
In what world is that NOT "seeing standalone stories again"?
And while we're at it, since when are crossovers a new thing? The SHOWS did them all the time! McCoy, Scotty, and Spock were on TNG, Kirk met Picard in Generations, the ENT-D visited DS9 in a TNG episode and also in the DS9 premier, O'Brien and Worf came from the ENT-D, VOY left from DS9 and later on in the series also met Barclay, Geordi showed up in a future episode... These people all knew each other already. The books have perhaps deepened those relationships, but it didn't establish them.
And finally, with the publication of Cast No Shadow, we will have learned of four of Vaughn's missions before he came to DS9. Out of a career of eight decades, is it really THAT unreasonable that, four times, he would've worked with other characters we've heard of? And is it surprising that those would be the missions people would more want to read?