I put it at a B.
First, regarding the prior characters and callbacks; I did feel like those were done well. Dodgeson had a definite reason for being, and the original cast had actual plot relevant things to do, rather than simply being cameo parts. The attack on the Jeep felt like a nice throwback to the original story as well.
However, this was an interesting film to wrap my head around. First, the story starts slow. We have three different groups essentially doing 3 different things and it takes a good 20 minutes or so of establishing the new world before there is really any "action" for our protagonists. However, once the kidnappings occur, the action element of the plot kicks up and the films pacing continues to move briskly.
I think where many will (or do) have problems with this film, is prior films are human vs nature and this one was more human vs human. Like the early Borg in Star Trek, the early Dinosaurs in Park were treated more like a force from which to escape rather than something that could be stopped/defeated. As the movie series progressed, the dinos became less intrinsically "scary" since they were established to be simply large animals; they were protecting nests, able to be trained, and our protagonists were consistently able to survive against them (even in the Park sequels).
With the exception of a few areas, this film doesn't try to make dinos the baddies. Rather, Dodgeson and GenSyn are the threat in the story. Even some of the dinosaurs chasing our leads in Malta could have easily been replaced with bad guys in black leather and motorcycles and it wouldn't have made an ounce of difference to the plot.
For this reason, the film was enjoyable as a kidnap, rescue, and bring down evil corporation plot, but the dinosaurs are definitely more of a background character in this story. If you are ok with the premise that the dinosaurs are now a part of the natural world to be protected as asserted in this film, then it can be quite entertaining. If you are looking for another "oh no, the dinos escaped from their cages" survival story, you are probably going to be disappointed.