Great article.
Let me rephrase the question like that:
Assume someone wanted to invest $1000 in crypto.
Would it be more profitable to trade altcoins, or to buy a miner and let it mine altcoins?
Some coins are quite difficult now, as you mentioned, and would be a waste of money trying to mine them. Some are still feasible.
The huge profits usually come at times of price spike, so he/she needs to sell only at those times. (most of the miners sell at once, converting either to btc or usd regardless of the current price)
in short mining is less risky than trading and can produce decent profits in some altcoins, e.g cryptonight and equihash algo coins, but trading in general would be more profitable, and more risky.