Really, my thoughts boiled down to explaining to this friend (who is primarily a Marvel reader) that the Ric Grayson arc was ~3 years of Dick Grayson being isolated from the rest of the DC community due to amnesia. Tom Taylor and Bruno Redondo were the team who were getting Nightwing back in the saddle, which resulted in Taylor putting a heavy emphasis on Dick's connections to the greater universe. There is a lot of Babs, since she's one of his most important friends and a long term romantic interest. There's a good amount of Steph and Cass, since Babs was also starring in Batgirls for a while, which made casual crossovers easy. Tim would pop in and out. Taylor also wrote Son of Kal-El, so there were a few crossovers with Jon Kent. There are Titans appearances/stories. I think these were all very intentional responses to the preceding era, but a common resulting complaint is that at times Nightwing felt more like a "buddy book" than a solo. There were also criticisms that characters weren't being used to their full potential, which tbh is just a weakness of teamups in general. Nightwing also crossed over into several events during Taylor's tenure: Fear State and Knight Terrors and Beast World are the big ones, but Dark Crisis happened in there, as did the more casual aforementioned crossovers with SoK-E and Batgirls.
I think another thing that Taylor focused on was a more slice of life approach, aiming for something a little more fluffy and wholesome than the book's previous tone (and indeed, the tone of most Bat-books). This had mixed reactions from fans. Does it make sense as an artistic choice, to tone shift away from the grim and grittiness of getting shot in the head and forgetting everyone you love (and rejecting their attempts to be in your life)? I think so, but that doesn't mean that people will like it.
One of the other big criticisms that folks have (which admittedly I wholeheartedly share) is the pacing. Maybe it's because of the fluffier approach, maybe it's just not Taylor's strength. I think this book moves so slowly. The "big bad" was introduced two years and 34 issues ago, and in Heartless' 14 appearances he has done only slightly more than nothing. I think part of the pacing problem comes from the events, in service of reconnecting Nightwing to the broader universe, but honestly I don't think that explains enough of it. The pacing is... choppy, let's say.
I did specifically praise the art, because this book's art has been so good. I will sing the praises of Bruno Redondo's work forever, and even when he departed the art stayed consistently good. And as I've said elsewhere, I really like the more bold artistic experiments that Nightwing has done. #87's "single panel" approach was SO cool. #105's "first person POV" was additionally a really interesting approach. Neither are something that I think would work for every issue of a run, but I like that these issues celebrate the artistic medium and do something so interesting.