Some things require a crew to do expeditiously. Like a roof. I won’t be replacing a roof, because I live in a rainforest and you have to work around good weather windows.
Single-handedly, I’d finish exposing the wood just in time for it to get rained on, realistically.
Gutters? Gutters generally suck. But the question to ask yourself is this: do you want to buy modular vinyl shit at the big box store and install it yourself, or have the gutter truck with the sheet metal vending machine roll up and customize to your house?
The question isn’t always just labor. There’s time constraints, and specialized equipment that also factors in to many trades.
Replacing windows is worth DIYing, though. Don’t get scammed by “renewal by Anderson” or anything like that.
Read up heavily on proper weather sealing.