Doesn't count as anonymous because 80%+ of the utxoset is owned by entities who mined them before it became public and global, which means that those entities can deanonymise pretty much all future transactions.
Marketcap is irrelevant as it's easily inflated (doubly so when all you have to do is slightly bump the price due to the massive amount that's already emitted).
That's a valid point, because when you mix you'll randomly mix with them 82% of the time.
We can actually work out the probability of transactions being 100% transparent to this hidden party.
Mixin of 1 would be transparent 82.2% of the time.
Mixin of 2 would be transparent 67.2% of the time.
Mixin of 3 would be transparent 55.1% of the time.
Mixin of 4 would be transparent 45.2% of the time.
Mixin of 5 would be transparent 37.0% of the time.
Mixin of 6 would be transparent 30.4% of the time.
Mixin of 7 would be transparent 24.9% of the time.
The more you mix with, the more transactions cost and the more storage it requires.