Earlier quoted context omitted.
Love this post, but I'm going to argue against one of your points: If it's a "trend", it's too late I disagree. In fact, if something is a trend, it's a guarantee that a market (of some kind) exists and it can save you a lot of time and research. Most big markets have large numbers of high value competitors and they're not all pioneers. Indeed, most companies with significant turnover were not pioneers in their field…
That point could really be a post all by itself and it certainly varies situation to situation. Semantics + defining "what's a trend" also play into it. There's mass market everybody knows about it trends and then there's emerging trends. The mass market trends ones are the ones to avoid like you said. The good thing is what you said: market exists. There's money there, just make sure it isn't all taken up already.
The market very often has been there quite a while with major players in it that are concentrating on monetizing their current offerings while being completely blind to the fact that new possibilities are now available. This tends to happen to startups that have "matured", generally replaced all their leadership and now have very little internal vision.
If you can spot one of these opportunities it can be a true goldmine.