Anyone can still solo mine UNO. That has never changed.
Assuming you mean mine
only Unobtanium (rather than merge mining it with Bitcoin) then you are right, but I would bet hardly anyone does any more. It would be much the same as throwing your money away.
Which basically encapsulates my concern about merge mining - UNO mining is now basically tied to Bitcoin, and if there is an issue (as per a few posts up) pools will drop UNO from merge mining, not BTC.
UNO has always been tied to bitcoin. Every Sha256 coin is tied to bitcoin because they are in competition for the hash. Miners will mine the most profitable coin, whether Bitcoin or something else. The nice thing about merge mining is that bitcoin mining (and by default UNO mining) becomes even more profitable. Merge mining is good for miners. Its good for Bitcoin. Good for all Sha256 coins. Good for Bitmain.
Well, I think we will have to agree to disagree on this point.
My concern with merge mining is:
1. it drives the difficulty sky high
2. the high difficulty means the only practical way to mine is merge mining
3. because the vast majority of miners are merge mining, their primary interest is Bitcoin and not UNO (or indeed any other MM coin)
those three points together lead to two consequences:
A. in the event of an issue with merge mining, the miners/pools will drop UNO (as we have seen)
and
B. because the merge mined coins are effectively "free" they can and will be sold at very low values