Newborns I found incredibly easy. No, they don't always sleep much, they cry and they poo, but they also don't take much mental effort.
My husband was around, and we were very much an equal team, which probably helped, but I actually felt more rested then I had done on years.
My first slept great by 6w, though it didn't last (and she's still doesn't sleep through 5y later)
Older babies and toddlers I found much harder tbh - but newborns, meh, I strapped them to me and kind of just got on with life, and had an absolute ball!
But everyone is different.
How you find it will depend on many different factors. Level of support, your MH after birth (PND will obviously make it a lot harder), the 'type' of baby you get, your strengths/weaknesses in the 'new job' (some people are better at babies, some toddlers, some older kids etc), whether you are used to living on rubbish broken sleep, or whether youve historically struggled with less than a full 8hrs etc.
Think about any new job - 10 people could start it, and you'd get 10 different answers about how they found it. Having a baby is similar. To done, it'll be the hardest thing they've ever done, an endurance battle initially. For others, it might be the best and easiest time of their life. Even the same baby, people will have a different view on how easy that baby is to parent.