As Picasso once said “Good Artist Copy, Great Artist Steal.
What is good is good no matter the artist. But it is the combination and how it is incorporated into a full package.
Harley Earl went to Paris and stole the grill from a Ferrari at the show to use in a 55 Chevy. No he physically did not steal it but he did take the styling and made the Chevy a major chassis.
The styling of the Cadillac fin started from a Lookheed P38 fighter.
The Stingray was stolen from the Fish of the same name inspired by it’s looks.
Generally most great designs are not 100% original. They are seldom practical. They often lack ergonomics and vision sight lines.
Yes often you have to pay the price to have great styling.
Today we are loaded with CUV models snd small cars and with the regulations for aero, crash standards where they have to have crush space between the hood and engine now. There are more issues but it is difficult to build a car today.
Also to step out to take a risk on a new style can be a very expensive risk. This is why Retro styling took off as it was safe but with no risk there is no gains to create the next future classic.
The box to work today is very small. Aero is a problem. It eliminates much and with EV coming a small element can cost 10 miles in range.
Other things today. The green house today has to be wider at 5he front and narrows to the rear. We can not drive with a rear window open on one side due to the air pressure from the aero flow over that window.
I wish companies would take more risks but will billions at risk the risks will be small.
Yes I have told several of my bosses over the years that they were wrong. Most of them understood when I explained it to them. Not guts no glory or continue to work for a jerk.
Someone up thread commented about the Audi TT. Consensus is (full disclosure, I drive a MkII TT!) that the original is an absolute copper bottomed design classic. When it came out it was a sensation - there was simply nothing like it. I prefer the MkII (obviously!) as I think it's a lot more dynamic and aggressive, and the less said about the MkIII the better (some extremely questionable surfacing around the front and the DLO kink in the C pillar looks out of place).
Small side windows are for aesthetic reasons, but it can be taken too far. Designers always consider bodyside to glass ratio - too much body will make the car look heavy and slab sided. There's a lot of regulation around glass area and visibility, mirror sizes and viewing angles etc.
The main way impact regulations affect appearance is hood height, as there has to be a certain gap between the hood and any hardpoints underneath (in case pedestrians end up on the hood of the car), and the size of any vent openings (so they don't break legs). Things like grill inserts have to be plastic so they will break, but this is more of a perceived quality issue than an appearance issue (press the grill on a Bentley and it's plastic...).
The Lexus LC500 is probably one of my favorite designs currently on sale. It's proof what they are doing can work, it just needed the appropriate canvas. The rest of the line up is an overwrought mess of too large grilles, clashing feature lines and twisted surfaces.
I would say styling is not the only thing that sells cars. Toyotas and the like have a lot of other qualities their customers appreciate (reliability, value etc), even if their appearance can be challenging.
You're right in that a lot of mainstream manufacturers tend to follow each other in terms of design. I think that's due to the fact the margins are so slim and the need to sell cars so great they have to play it safe and do what everyone else is doing.