I barely even noticed they got replaced. They never got to have any story involvement or character development, just like most of the rest of the bridge crew in Discovery.
I really found the coda/epilogue to be distracting. The end of the main story ended in a good place, with Burnham and Booker heading off on their next adventure. And then suddenly we're getting this long drawn-out "and then later after many adventures they... did something useless we can't explain but at least they saw their old friends again the end" just really took the wind out of it.
