I think he's going through a weird phase right now. After being Tony Stark/Iron Man for 11 years, he's now looking to prove he can be successful outside of the MCU again. Chris Evans already has done this with Knives Out, Mark Ruffalo was great in Dark Waters and ScarJo put together a case for best leading female and supporting female this year with her performances in Marriage Story and Jojo Rabbit.
Dolittle was the film RDJ had lined up post-Endgame and if this was his pet project, then more power to him. But production issues lead to an inflated budget and what looks to be a fairly mediocre movie. Then all of that led to a January release date - a death sentence for any wide release movie that isn't nominated for awards. I also realized it's not a guarantee that this movie even releases in China. Isn't there a 20 film limit per year that China can release that aren't Chinese domestic films? The Chinese government chooses which films release there and this one may not make the cut.
It can be jarring going from incredible stability for so long to now having to once again prove yourself to Hollywood.