I would say yes, sorta. It really depends on the game dynamics like how many people per server and how many structures. For the games start I would say yes it is a bit big. Start small as you can always add more later.
Also side point: I would make a small area to find your theme and add details before making a huge base! Hope this is helpful good luck. <3
Yes open worlds are amazing, its really up to you but for the sake of time sensitivity and preformance I would start smaller (not much smaller) to put more effort into it.