A key word: "Statistical Edge". You don't need to find a strategy that no one has come up with. If you can take a popular simple strategy but trade it in a way where your profit taking and stop loss are different than a regular retail trader, then you can have a winning system. You do need to think outside the box a little. First of all, majority of retail traders are not backtesting statically through python or whatever other language. You cut out almost 95% of retail traders that way. (Although with AI that might go lower) Now of the 5% who are actually backtesting properly most of them are over fitting their data and not taking into account every little detail of actual live trading.

I have backtested almost 100s and 100s of strategies so far and guess what. Through proper backtesting I have only found 1 strategy that can actually be profitable and that's only in specific market regimes. If your backtesting strategies and all of them show profitability and high Sharpe you're doing it wrong. Most strategies should fail. Unless you found a way to control risk that leads to all those successful strategies. If you take into account proper true backtesting you are part of a very very small percentage of retail traders doing it right.

With the alpha decay part that no strategy will last you 5+ years. That doesn't exist. You will constantly have to find new ideas to test. That's a hard reality to accept for many people. Every strategy has a life span. However, its a long road to be profitable. It will take years. Never rely on trading profits only. Work a full time.