I'm not that close to MWR as you are, so that's why I add the phrase with "my impression" as a precaution



But before I (completely) surrender, let me still put in a few remarks:
Isn't it true that MWR had (at the end of the 90s/beginning of the 2000s) about 1000 species as well (close to 700 species at Jurong Bird Park, more then 300 species at Singapore Zoo AND Night Safari)?
I have no doubt that MWR has now more invertebrate and fish (and maybe also reptile/amphibian) species after River Safari/River Wonders has opened its doors. Also, the new small(er) mammals from South America for RS may have equalized the loss of the small(er) mammal species from SEA at Night Safari and/or Singapore Zoo. But what about other (=bigger) mammals species? About a dozen of ungulate species are phased out (e.g. Red Hartebeest, Black Wildebeest, Springbock, Impala or Kafue Letchwe to name just a few), as well as many crocodilian species and also important species for common visitors like Pumas, Mandrills, Polar Bears and soon Asiatic Black Bear are/will be gone. In the meantime, only Giant Pandas came into the collection as big(ger) mammal species. Also the rare-in-zoos cape subspecie of the giraffe was replaced by boring common subspecies.
I can (at least mostly) understand the steps of the MWR Mangement in this point. However, I stay with my statement, that for me, Singapore Zoo and Night Safari are less attractive compared to my first visits about 20/25 years ago. On the other hand, those institutions belong quality wise - again: for me - still to the best zoological institutions in the world. And I hope that, after Rainforest Park and the new Bird Park are built, MWR will let my forget my concerns I have at the moment.