To an extent, I understand why so many people who oppose socialism use language that condemns equality of outcomes, but supports equality of opportunity. The idea of equality of outcomes is something that can lead to nothing but unfairness and suffering. It's an evil idea that has to be rejected at every turn.
That said, the word "equality" is attractive to people. There's a reason what "all men are created equal" is in the preamble. Equality of outcome can be read to be supportive of good values; but, I still think it's a dangerous idea.
Really, equality of opportunity was what the dystopia depicted in Harrison Bergeron. If you're too strong, we shackle you. If you're too beautiful, we make you wear a mask.
Maybe it would be nice, in the minds of some people, to have a level playing field wherein only merit, rather than certain advantages that you have, that really can't be trained. I don't think that that's possible, nor desirable.
Equal treatment under the law is obtainable, and desirable. Treating people fairly is something that we should strive for. I'm not sure why these concepts aren't at the forefront, aside from the fact that some people deserve to be treated better than others. If you're a dick bag, and you're treated fairly and equally, your life is gonna be a lot worse than it would be with equality of outcomes or opportunity.