Seeking advice – How do you make money longterm on Amazon?

I am relatively new to Amazon few years just dabbling with a couple of SKUs. I am seeking the advice of some of the more established Amazon sellers here. What is the overall strategy you guys take? It seems that once you find a high demand low supply product and bring it over from China for example it doesn’t take long before other sellers do the same and you end up fighting with them over customer traffic, dropping the price to remained featured at Amazon and spending lots of $$ in amazon ads to get clicks. It keeps getting worst and worst with time that at some point if feels like only Amazon is making money.

So what is the point? Do you guys focus on making quick cash while the category is still not a blood bath or is there a way to actually thrive long term with private labelling even though there are very low barriers to entry?

I would appreciate any advice, at this point it seems like there is no way to make real money on Amazon.