I did not say *not* to trade forwards.

But thanks for the addition anyways. However, if you look at the retail space where traders might not have good access to these instruments, you can trade CFDs and still earn carry. Not sure about the US to be honest, but these are easily available in Europe. Take OANDA, for instance. They'll charge negative carry if you're short the higher-interest CCY, but they'll pay positive carry if you're long that CCY. Of course, there's a spread.
Also, as you mentioned yourself, while your earnings from carry (positive or negative) are almost certain ex ante for short periods such as overnight, the total return from your position is anything but certain given the fluctuations in the exchange rate. To repeat myself: This really is no arbitrage thing.
I can't confirm this for an institutional setup, but I won't say you're wrong b/c I don't know how futures are being priced by brokers in the retail space.
I guess you're talking about what you mentioned for futures above. But your statement is not entirely true as-is: If you buy a high-interest CCY, that CCY actually "tends" to depreciate *less* than the carry or even appreciate! That is why the carry trade is still employed as a popular investment strategy. It's only during risk-off scenarios that the trade falls apart spectacularly.
I agree with everything you write except for the final sentence. Earning carry is no illusion. I'm doing it via forwards every day (and in the retail space, this works with CFDs too). If you buy TRY and sell USD, for example, and at the end of the day your broker has taken the entire carry from you, get another broker! Seriously, the carry in the forward market for USD/TRY shorts is 14% p.a. as of this writing. No broker margin should be so big that it uses that kind of carry up completely.