Should I back up my iPhone on my MacBook Pro?

Absolutely it is good to backup up a phone to the Mac but make sure you have adequate space on your Mac to store everything. If you don't, or even if you do, Apple's iCloud backup for iPhones works well and takes no space on your Mac.

Backing up an iPhone to a Mac works fine.

Biggest concern there is whether you can remember to back up the iPhone sufficiently often, or on some set schedule.

You’ll want to back up the Mac too, of course.

if you have anything valuable to you on it, yes, make a backup. and it's so easy to do, why would you not want to?