The point about it being a scam for the early adopters to profit at the expense of later adopters is like saying that IPO is a scam, because people who bought shares at the time of the IPO are profiteering of those who bought their shares later in the game.
Early adopters take most risk and therefore reap most benefits.
But there was not really much risk early on. Worst case you burn up a bit of CPU. The question is how much of a benefit should they get just by being an early adopter (rather than a developer or early investor)? The developers put a lot of time into it so they had a decent amount of risk (wasted time). Early users really didn't risk much by using it (what is the yearly electricity cost of using the software).
If 90% of the coins were held by the first 10 people to ever use Bitcoins, that seems like a system that is not terribly useful. Perhaps what we have now is ideal. Perhaps it was too generous to early adopters. Having too much in the hands of a few people makes it unstable since they have a huge influence on the market and their whims control a huge amount of supply.
But in no reason does it make it a scam.