What would you have done differently? All healthy languages need to constantly evolve, you only get to decide where. You can change syntax, add keywords, attributes, etc but it's a tradeoff.
Any attributes or keywords relating to Objective-C or interop are not everyday baggage for most people.
For SwiftUI, attributes seem like as good a choice as anything else.
As a whole concurrency is a mishmash syntactic mess, but I agree with the direction and the result, they're trying to manage the improvements they keep adding over years of investment.