An early adopter will always have an advantage over somebody who gets on board later. The only way you could prevent this is by actively punishing early adopters. Good luck achieving adoption if you try this.
Bitcoin doesn't punish late adopters, it just does not give them the same advantage as the earlier adopters. Somebody who adopts Bitcoin today will still have a major advantage over somebody who adopts it in 10 years from now, but it might not be of the same magnitude as the people who adopted it 10 years ago have over the people who adopt it today.
The decline in rate of inflation is what prevents punishment of the older adopters. Inflation is inherently punishing of people who are saving an asset, because it steals value from them, or at least would do if demand didn't outpace supply.
If bitcoin offered the same reward to newcomers as it did to the people who adopted it 10 years ago, then nobody would've adopted it 10 years ago, and the result would be that everybody is punished, because the world at large would've ignored a great innovation.
You can't have both! Either you punish the savers by taking value from them and giving it to newcomers, or you let savers keep their value which pushes up the price for newcomers as demand increases. Socialist ideology fails to understand economics as usual.
Now you might argue that the rate of bitcoin's reduction of inflation is just too high, and should've been more gradual, or over a longer period of time. There might be some merit to that idea, but nobody could've accurately guessed the rate at which adoption would occur for a brand new technology.
After everyone is aware of what Bitcoin is, it doesn't really matter how long you make the halving. There will still be risk-takers and there will still be laggards. Some of the laggards will leave it until they can no longer go around with their eyes closed and must acquire some Bitcoin in order to make some purchases. Others will acquire it now (and 10 years ago) even when it is an extremely risky investment. Most people are somewhere in between.
So you have the option right now that you can either: Acquire some Bitcoin while it is apparently still cheap (relative to where it may be in a few years)
Or you can: Chose not to acquire some bitcoin because you think it is overpriced, and in a few years, complain again that bitcoin is overpriced, when it is worth significantly more than it is today.
Late adopters punish themselves by ignoring economic reality, either intentionally (because they are driven by ideology), or accidentally (because they don't take the time out to learn). Once you grasp it, there is only one direction which bitcoin can go over the long term.
