Umm I can think of any number of episodes, including a recent movie where Star Fleet members were one of the chief villains.
Over the years there have been a number of good scifi shows cancelled and in interviews after the show the same reason is regularly cited for cancellation, that is, the special effects and constant new set changes are just too costly per episode.
I wouldnt be surprised in the least if this is the thought process behind the change because how much can it cost to rearrange a bedroom once in a while? The same ship hallway that the sponge head alien was killed in in a hate crime this week is perfectly suitable for the next weeks episode where the captain rapes the green alien girl.
In other words, someone has decided to kill the franchise to try and get rich quick and weapon will be poorly casted and written sex and murder between the crew.