I am making ~$145,000 per year and was wondering if it is wise to contribute 12% pre-tax to my 401k? Is this too much? Is there any disadvantage in contributing nothing? I am already well off (come from a affluent family) so is there a point in even contributing to my 401k?
In my opinion it's not possible to contribute too much to a 401K. (Unless you don't have enough money left over to pay your bills.) The max you can contribute in 2020 is $19,500. The main reason to contribute to a 401K is because of the tax savings. You can choose to put money into a traditional 401K and pay less taxes this year by deferring that tax, and also the tax on all the growth, until after you are 59.5 years old. Or, you can not reduce your tax this year and put the money into a Roth 401K and then you'll never pay taxes on that money again; even its growth is tax free.
In your position, if you don't need the money now, then I'd recommend maxing out the Roth 401K with $19,500 this year, and investing it so that all of it and its growth will be tax free once you reach age 59 and a half.
The disadvantages to not contributing to a 401K are that you lose out on the tax savings just mentioned, and, if your company has some amount of matching, you would miss out on that too.