Its still a thing (as others have mentioned ETH) but its not quite the same as 2017/2018. Back then new shitcoins were popping up daily, along with a steady stream of coins that may be more profitable depending on what GPU you had. Those days are pretty much gone. A lot of those coins went to asic and there isn't the influx of new coins. Right now ETH is about the only game in town if you have a card with more than 4 GB of RAM.
Ethereum was gaining ground fast when I stopped mining. It was already becoming the most profitable way to mine, while the other algorithms (I remember Decred and a few others) were starting to be unprofitable to run older rigs.
It's kinda too late to build a mining rig right now because does graphics card have skyrocketed in price, it's like using the money that can buy 3 graphics card to buy one right now is just better to invest your money in altcoins rather than thinking about getting GPUS for mining..
Incorrect
I'm not quite sure if I'd build a rig now for the whole purpose of mining. My PC has a malfunctioning motherboard and could use some upgrade, in the meantime, my laptop doesn't meet my needs. Thus, I could combine these two needs to mine and simultaneously repair my computer.