What kind of challenges are you looking at? scenery modes have the challenge of making you meet the objectives and timed scenarios have the bonus challenge of making it on time, while franchise and challenge need you to overcome problems such as animal stress and animal populations growing or shrinking, and the lack of specific animals on franchise.
And yes, i agree that it lack managing in this game, but let's be fair, sandbox on release was quite underwhelming as well, and it's only "good" right now after frontier update it 5 times, while all the other modes and managing aspects where left to rotten, so maybe it's time to left sandbox to the side and work on everything else.
Im looking at no challange cause there is none.
All actually challanging aspects of the game are tied to building with things like layout, design and guestflow, which are mostly just cosmetic anyways.
Currency is invalid, get 2 tortoises, press speed up, go afk for 2-3 hours and your swimming in money and cc.
The market is inflated to a point of tedium, where you have to pay max price for mid animals, creating an artifical barrier for new comers but just a little annoyance for those that allready have a franchise running.
The game is way to fast to allow for any micro decision making and some animals just die like flys.
Putting a timed mode in a game about building is just nonsense, the games strenght is in building so why am i punished for actually taking my time and making stuff pretty?
The only mode i cannot completly bash are the careers, cause while i have 0 interest in them due to prefering freedom in my builds, i can defenetly see that their handholdy nature would help players with a lack of direction.
Its boogus that i have to play them against my will for the very usefull animal statues, but thats another issue.
Now sandbox, that mode does what it says, actually alligns with the game strenghts and even allows to enable everything you do like of the "Management", easily the definitive mode of the game