The stock market for the retail investor is a zero-sum game. You win at the expense of another. Your success depends on being skilful in the way you invest.
Fundamental and technical analysis are very different approaches. With fundamental analysis you are looking at the factors that drive the profitability of the business. With technical analysis you are looking at crowd behaviour or market sentiments.
Both requires different analytical skills and behaviour. Imagine trying to be a capitalist and communist at the same time to solve socioeconomic problems.
It is already very challenging to develop the expertise for one investing approach. Now imagine trying to be an expert in both fundamental and technical. I would think it is tougher than focusing on just one.
Having said that, once you have mastered a particular investing approach eg fundamental, you could complement it with the other approach. So while I am a value investor, once I have identified a target, I use technical analysis to time my entry. But I never forget that my entry is because of my fundamental analysis.
Along the same line, if you are a technical investor, you could improve your trades by having some fundamental perspective. This is the main thrust of my updated post this week aptly titled "Can you make money trading with fundamentals?".
I gave examples of famous traders who have successful traded using fundamentals