The profitability of mining altcoins solely depends on how long you are going invest and mining the altcoin. But the best site to help you calculate your potential earnings within a day or months is
https://whattomine.com/coins.
Let me answer for you with your own post
In terms of market value, I will agree that most altcoins are worth zero. Some are just in the crypto ecosystem to occupy space. Some of these coins have no specific purpose that aims to help the crypto ecosystem solve gaps in this ecosystem.
I did not see how whattomine telling you this
and i think you really have no clue what you are posting about
Ethereum mining is a long term investment plan. If you invest in getting a mining rig which can mine at least 4 ETH within a day and you dedicate at least two good years mining ethereum, you will be having 2920 ETH which will be very profitable even if the price of Ethereum is worth $100.
Let me guess...
you used whattomine to calculate your potential earnings for the next 2 years
, but forget about Ethereum's intended transition from PoW (Proof of Work) to PoS (Proof of Stake), forget about difficulty bombs, difficulty growth and a few more important things
... Yeah your mining calculator forget about all those small details
oh..by the way ...
there is no mining rig available what can can mine 4ETH a day for 4 ETH / day you need around 12000MH/s as of today
so you need around 50-60 mining rigs for that and a minimum of 60-70kw/h electricity available and some place to install your miners