There are some people - and I get the impression that
@Essayist of History is one of them - who derive great pleasure from being contrarians who always claim that anything great must actually be less than we perceive it to be. That is very nice, and even healthy to any debate, but I have noticed that at a certain point it becomes less than constructive. Scepticism can be so far extended that it becomes a dogmatic denial that anything great could even exist.
The fact of the matter is that Alexander was preparing to invade Arabia when he died, that he had soldiers in sufficient number to see it through even if he suffered losses in excess of 50% (which would not have been the case, as he only really sought to control the coastal trade ports), and that he was building the greatest fleet the region would ever have seen. He controlled the treasury of the Akhaimenid Empire, in which vast sums remained, which allowed him to finance this without any serious issue arising. The tendency to negate anything Alexander might have achieved is based purely on the unwise behaviourism I have outlined above, and has little to do with any facts. It
is true that Alexander's life-style was dangerous, and it indeed likely he would have died quite soon after his OTL death if he kept it up. This is countered by the fact that the very arrow-wound he received from the Mallians really slowed him down. To the extent that he was planning to travel by ship during the Arabian campaign, letting others command the two armies sent down both sides of the peninsula. This is something he had never done before, and rather shows it was finally getting through to him that he wasn't immortal.
If we assume the premise that (by pure chance) Alexander lives long enough, the scenario of his overwhelming success is hardly out of the question. It's a matter of momentum. Once you get a certain thing in motion, it just becomes very hard to stop. Once you establish an Empire that cannot be defeated by any external foe, that Empire will last until it fails internally. (See: Toynee, Arnold.)
I'm quite sure that after conquering Arabia, Alexander could have taken Carthage, Rome and whatever other states he wanted in the Western Med. They were absolutely no match for the power he was able to project at that point. Observe that the greatest danger would be "the other end" of his empire revolting against him, but that actually, he was quite beloved in Persia, and all insurrections in OTL happened in the West (and at times he was far away). With him in the West again, his Empire was quite secure. (Observe also that the oft-raised matter of Chandragupta would be a non-issue: Chandragupta invaded
because Alexander was dead and his successors were in-fighting. Facing a united empire, he would be far too smart to risk that, which can be supported by his typically calculated manner in OTL.) I state again: Alexander's Empire is at this point secure and in order. His further conquests in the West will only generate a broader tax base in the future.
Then we get to science. Here we also disagree. While Russo has a distinct tendency to over-emphasise and to go on wild speculative tours of the imagination (he bases one "could have" on a previous "could have" more than once), he does point out very real developments. We can say, without distorting or exaggerating anything, that there were Romans in the late first century AD who commented on Hellenistic math dissertations-- and their commentary illustrates that they failed to fully understand the math! Knowledge
was lost. Russo's problem is that he imagines the Hellenistic World was at the very edgo of an industrial revolution, which is clearly wrong. And indeed, not only Greek (or rather broader: Hellenistic, ehich is not
just "Greek") insights were advanced, but the Indians and the Persians as well. Thing is... Alexander had just annexed Persia, which would put Greece and Persia in one polity... which bordered on India... which was (per his explicit plans) set to invest in infrastructure... which would further the exchange of knowledge.
My claim is that this would benefit science and technology. Not leading to a scientific revolution right away, but quite realistically bringing it much closer in time. After, say, a few centuries to a millennium, we might see such a thing. That's still much sooner than in OTL. And that's not the radical kind of claim Russo makes.
Now, needless to say, a habitual contrarian will reject all of this out of hand because of a dogmatic belief that it cannot
possibly be true, but any somewhat objective observer will realise that this is not so strange an outline I have presented here.