An awfully long way to go for a fly-by. I would have hoped for orbit.
A capture trajectory probably would have taken too long. It’s already been flying for 9.5 years, and without a gravity boost from Jupiter it would have taken another three. Carrying enough fuel to “deorbit” probably would have required jettisoning 3/4’s of the instrumentation. New Horizons is definitely a compromise.
It will take months to send back all the data it collects. The trade off between comms bandwidth and instrumentation favored instrumentation (with on-board storage). Same problem, bigger antenna, more powerful transmitter, would have displaced other instrumentation. Storage is cheap, compared to bandwidth.