Did it ever strike you that the Mac mini design is intentionally not updated for 12 years? The single most common use of Mac mini is in installations that are literally built around it's form factor - rack mounted in server racks, mounted to walls or desks, mounted behind TVs/Displays, embedded in various custom enclosures, etc. Having a new model use the same form factor is literally a critical feature for these types of setups. If the form factor were to change, many installations would be cost prohibited to upgrade - not because of the cost of the Mac mini, but because of the cost of retrofitting or completely redesigning their existing deployments.
iPhone SE is a niche phone for a niche market and it suits that market incredibly well. By retaining the same form factor but upgrading the internal hardware, they are saving vast R&D costs, materials costs, and even manufacturing / machining costs. This is a win-win for everyone involved.
Mac Studio - boring? The hardware is unmatched and unexpected. The design is very minimal and pleasing. It's designed perfectly for the intended audience.
Can you give an example of what you would suggest or expect? I think the 3 products you called out are 3 of the products Apple sells that have the narrowest audience. Consequently, I actually feel like these 3 are among the absolute BEST designed products for their design goals.