This may be an unpopular opinion, but here we go. It depends on how you define "startup". There are two common definitions, and people confuse them all the time and don't make clear what they are talking about. 1. A VC-backed company whose primary goal is exponential growth with a small chance of an outsized return. 2. A profitable business.

If your goal is to do the first, then luck will play a large role. That's why VCs have portfolios of companies. It's nearly impossible to make predictions about which startups succeed, but if one of their companies does, they win (note that they don't care if it's your company or not). As a result, VCs push their companies and founders towards making risky bets. Those bets involve a large amount of uncertainty and randomness. You either win big, or you lose.

If your goal is to build a profitable business not focused on exponential growth or VC-sized returns, then luck plays a smaller role. That's because you are not forced to make those large risky bets. You can take more calculated risks with slower growth while focusing on profitability. If you win, you are not going to win as big as in the first case, but your chance of winning in some way is higher. Of course, there is always uncertainty in life.

Note that I've focused on financial returns, which may not be what you (should) care about. For example, your chance to fail is high in the first case, but you since you are involved with more "successful" people you will likely learn and build a network along the way that can set up you for future success. You are more likely to "succeed" in the second case, but you may not build much of a network or stretch yourself. Similar arguments in the other direction can be made for mental health or stress levels.

I recommend reading "Fooled By Randomess" [1] on the topic of chance

[1] https://www.amazon.com/Fooled-Randomness-Hidden-Chance-Marke...