1) Lack of originality. They can't think for themselves. They end up copying from a company regarded as having good style, Apple. The only problem is that when Apple went Material Design (a/k/a) Moronic Design it was boring, bland and 2 dimensional. But that didn't stop the lemmings from jumping off the same cliff. MS followed with the hideous tile interface that they are still forcing on people in Windows 10. I don't know what the rest of the world thinks is attractive, but to me it sure isn't stupid monochromatic squares everywhere.
2) Lack of taste. This is exemplified by Material Design.
3) Lack of willpower. Not having the will to do something different, something that isn't derivative.
So does this mean if Google changes Chrome again on how it looks that Firefox will follow suit and do the same since that is what they did last time Google changed things up and yes I use Firefox so not being a Chrome fanboy I like firefox over Chrome personally it is a bit faster than Chrome. Well it used to be before Firefox Quantum that is.
Is it just me or do the new tab shape look exactly like Firefox? Currently it is very easy to tell if someone is using Chrome do to the different shape tabs. Now Chrome will just look like the other browsers. How sad.