Sorry mate but your arguments make no sense to me.
First I don't understand how, even with the current "crash" on the altcoin markets, your profitability can be declining rapidly. All coins have doubled/tripled (and more) in value within the last few months. Even if you mine less coins, the profits are still huge compared to last year. So unless you pay 1$/kWh...or I'm missing something.
You're missing the fact that difficulty is skyrocketing because everyone, their mothers, their grandmothers, and their dogs and cats are jumping into the gold rush. Take a look at any of the profitable coins' hashrate and difficulty charts for the last couple of months. They go from a gentle upward slope into an abrupt near vertical climb. So as more people/hashrate come into play, everyone's respective piece of the pie shrinks unless coin prices keep rising at an equal or greater rate.
I'm not missing this at all mate. We've had one of the biggest booms in cryptos in a while over the past few months. I'm making more than 10x the profits I was making last year at the same time, hence I don't get the "rapid decline" the other poster was talking about. Agreed I'm making less than a month ago because most alts are traversing some uncertainty, but the profit I still make today make me very happy.
You can't really blame every last person to jump on this. A lot will regret it though, imho. I still think profitable PoW lies ahead for those who plan things carefully.