With the way you address people on here and the confidence you show, than I am sure you know the base underlining price structure and patterns in the markets hasn't changed in a very long time (I know factually that it hasn't for at least 20 years). With that said while I don't personally use trend lines, it's not out of the realm of possibility that someone with enough market experience has learned over time how to draw them so that they do indeed get a consistent and quantifiable edge using them, particularly if they draw them on an underlining indicator and do not use price directly.
Trendlines are like marketing. When you market something you present a distorted reality and one may also present additionally pretty sexy pictures to get the juices really running. Trendlines are like that, because trendlines appear to work because a chart with a nice trendline shouts "look at me, I'm a trendline, look how much profit I just created". The other 80% of charts without any trendlines are ignored. One reason most traders fail is because they are caught by being fooled, there's a huge amount of randomness involved but our mind is trapped to only seeing what we want to see, the profitable trades.
If looking at the trendline statistic, 60% of stock that move above 50day MA cannot last for more than 10 days. However, those that can stay above the 50 day MA for more than 10 days, 30% will fail. Not much of a comfort. Just being patient and observing the "behavior" of the trend, one may be able to spot some winners.
An algo dominated markets is not what is stopping 99.9% of people on these boards from being profitable. You could trade 50-80 ES lots consistently and generally speaking you're still not going to attract any serious algo attention. That's way beyond what most people here will even ever dream of trading, much less putting that many contracts on at one time(not to mention you could even stagger those out as well if you were still concerned) That's just a talking a point and an excuse retail traders use. Algo's look to take advantage of temporary imbalances in market supply, which very often creates further imbalances due to the velocity of the move that the activity generally creates. For example during a forced short covering rally it will often create an overbought scenario which once the other party has capitulated price will very often mean revert back to where the algo activity took place.