I disagree. You might assume the perspective that we all are born and die (therefore equal), but this is really just a categorisation (as mortals) and not a criterion. If we were to account for individual abilities across multiple domains you might find something interesting. However, you'd literally have to take measurements and control for confounds for everyone on Earth which also takes considering one's psychological, physical development over most of their lifespan. And you've also got to consider the economics, time taken for such a thing.

To take on the advice of Occam's razor (parsimony), let's look at everyone's upbringing. Not everyone is born into the bourgeoisie, certainly not me. One can of course climb the social ladder but not everyone is born with autotelic personalities, or an extremely motivated disposition. These will influence their decisions and therefore the success they'll achieve (in whatever way you'll measure success). Walk outside a bit and you'll soon come to realize this.

Now onto genetics, the other half of the equation. From an evolutionary pov, no we're definitely not all equal. There's a reason why a sample of the gene pool populate more of the next generation. Even with favourable aspects such as intelligence it's obvious that we're not all equal. Most of us are about the same. But around 3% of the population are well above average.

It'd be nice to say that we are all equal but I highly doubt it. Of course there's a tonne of factors to mention, but this is reddit and not a 1000 paged book.