Correct, because everything is dynamic, including the search terms, eyeballs, and competition for keywords. It's pretty simple economics - once I find a way to spend $50 to make $100, it's only a matter of time before other people discover something close enough to make me spend $75 to earn $100. Then $90. Then (conjecture), winners curse takes account and people are spending $110 to make $100 (once Neil Patel's audience hears about it).

With the tactics being gobbled up by the Red Queen effect, you have to move to strategies to win. The OP writes about a pretty good one.