> Everything is a tradeoff and [designers] are the ones 100% on side of usability
Designers shouldn't be just 100% on the side of usability, they should be balancing multiple factors such as cost, aesthetic, durability, portability, accessibility, ease of manufacturing as well as usability (there are many more).
All of these things have trade-offs - making a product more durable might increase cost, making it easier to manufacture might hurt it's aesthetic, adding more ports might improve functionality but decrease the aesthetic and increase cost etc.
The job of a designer is to balance all of these factors. The argument is that the balance Jony had was skewed more towards aesthetic which resulted in trade-offs in other directions.
> The aesthetic is a side product.
IMO the aesthetic definetly isn't a sideproduct for Apple - it's clear that aesthetic is a core part of the design process (see the iMac G3, G4, Trashcan Mac, latest iMac, Homepod e.t.c. where a significant portion of product engineering is driven by the external aesthetic to a large extent). The design of the iMac G4 was no accidental side product of the tech.
The criticism of Ive is that he weighted aesthetic too high at times, which for example resulted in an obsession for product-thinness which compromised the usability/durability of the keyboard, and of un-obtruded sides which led to the removal of ports and a charge-port on the bottom of the magic mouse.
You can still be a great designer and have a bias towards form over function - and arguably the best designs are done where there is some sort of creative tension between form and function (as tension often breeds creative solutions to release the tension).