For those who worry about this, think of it this way. If your strategy had a positive expectancy before the age of robot algos, it was because your strategy took money away from another set of traders who had a strategy with a negative expectancy.
OK, now just picture that same set of traders implementing their net negative expectancy strategy as an algo, rather than manually. If your strategy still works, it should still take money from that set of traders, regardless of whether those traders are trading their net negative expectancy strategy manually or via an algo. How did those traders get the capital to create and deploy the algo? The same way they got the capital to lose in the pre-algo days.
If you can't make money now even though you did before, it's because the traders from whom you used to take money are gone. You either need to learn how to take money from a different set of traders or, like a pack of animals which has lost its hunting ground, you have to move on to another hunting ground.
At the end of the day, in a zero-sum game, you are either the negative part of the zero-sum or the positive part. How you implement your strategy (algo, robot, manually or smoke signals) is secondary to your strategy being smarter than at least 1 other person in the marketplace you're trying to profit from.
It's like the old joke about the two guys running from a bear, with the guy who's behind his friend saying "You can't outrun this bear" and the friend replying "I don't have to. I only have to outrun you". You don't have to outrun every algo, you only have to outrun one. If you can't do that, well, then you are no longer suited for trading.
It's really that simple.