1. For assets that come from income you yourself earned, the tradeoff is basically whether you spend the money immediately or spend it later. If you're going to have a capital gains tax, that tends to penalize people who don't spend the money immediately. You can mitigate that by at the very least inflation-adjusting the basis, but the US currently does not; I can't speak for other countries. And that still ignores the time value of money and discount rates, of course. But inflation indexing of basis seems like a bare minimum requirement for claiming that capital gains income is like wage income; otherwise you are taxing nominal gains that are not real gains.
2. For assets that come from an inheritance, there is an argument to be made that now this is no longer you just deferring consumption. It's still deferred consumption in the sense that whoever you inherit money from deferred it, but the moral argument becomes a little more complicated, because now you start having the basic moral argument about whether inheritance should be a thing at all. There are also the complications around basis step-up (which is, I suspect, there for practical reasons that may be becoming less and less important in a world where the record-keeping is outsourced to brokerages and the like more and more).
More generally, it's not clear to me that "income" is even the right thing to be taxing. A progressive consumption tax might be a better idea if what you want to tax is consumption of resources in excess of "normal". Unfortunately even small moves in that direction (e.g. luxury taxes that used to exist) have largely gone away in the last few decades. In large part under the flag of "it's hurting jobs in our state's industry".