This drama is being adapted from a female-centric novel so there has been quite a fuss about the ML, DylanWang/Wang Hedi/Whd, taking first billing.

Below is a post that explains the billing arrangement quite well (thanks @lily):

"Actually, there are rumors of big actresses turning down the offer of this drama cuz whoever takes it will risk her career and will be targeted by novel fans just like how it's happening rn for both leads. Whd already rejected this previously but now the ip was about to expire and xinli needed someone big quickly. Since they failed to get any big actress willing to work on this project, they approached whd again and convinced him by offering Guardians of the Dafeng S2 so he accepted... He attracts a lot of investment. He is commercially successful... Xinli is a production company which doesn't risk by taking small actors... This is S+ budget drama so investment and money to make this will be more so need higher return and profit and Xinli won't risk this. They need guarantee of it at least doing decent which whd & mzy together can give them. If whd is not the ML then the project investment will go down and budget will drop from S+ to S. This is how industry works and Xinli doesn't want to lower their budget for this project."

Regarding the ability to attract investments, Dylan's Guardians of the Dafeng broke records for the highest overall ads duration, 4311 seconds, the highest in all platforms in cdrama history. Please see details below:
https://kisskh.at/photos/l0ZrgQ_3 

Post from @Ti02:

"I don't understand the ruckus with the billing thing! As far as I know, billing has nothing to do with who has the more prominent or titular role! Like the story might be based on the male character or the female character, but that's not how billing happens! Billing depends on who brings the more investment, or who can shoulder the investments! For a S+ drama, they need an actor who can take the responsibility to deliver one, on whose track records, popularity, fandom, producers can trust their money! You can say its misogyny and the ones leading the project should be billed first, but that's not how it works, ig in any entertainment industry, this is business!
Novel readers can say a women lead novel being adapted to a drama with multiple changes, like making the male character more prominent, is bad! I don't disagree, but then the producers needed to cast a female actor who is more famous than Meng Ziyi. This is not a shade to her, I am just saying what I know, Wang Hedi is more popular actor than her.

My personal opinion- This will still be a story of a woman seeking revenge! They are just going to make ML's character a little more prominent. As someone who read the novel, ML in first 100 chapters wasn't really there a lot, so Ig they must have added him there! I feel people should just wait for the drama to release, criticizing it from the first day of shooting without knowing a single thing is really wrong! At the end, not everything is in the hands of the actors, there are bigger stakes involved! Billing first or second or last, if an actor is dedicated to their craft, they will do a good job! They already have a very good script, so let's see and hope they don't make changes that will ruin the script!
Rebirth plot is getting changed into a dream, because its China! I really think if they adapt it well, while giving prominence to ML's role a little more, it won't be detrimental! "