I have frequently found that the in game ATC either offers descents that appear to be way too early or way too late for an approach. Sometimes they get it right, however.
One thing that seems to mitigate errant descent profiles is to have a predefined STAR and APPROACH selected as part of the flight planning on the world map before starting the flight.
With regards to the slowing down while on the glideslope, my own experience with the 787 is that autothrottle usually slows the aircraft when approach is activated and I keep lowering flaps. Every flap deployment seems to reduce the speed further. However, I tend to use manual speed selection on approach, with A/T engaged, so I decide the approach speed, if that helps.