I’d wager that if founders were to dig deeper and were to be honest with themselves, they’d find that many of them start startups not motivated by some lofty mission to change the world/make it a better place.
Beyond having an idea and wanting to make a product or sell a service that you think is better, the reasons to start companies can often be more personal (selfish even) – a personal desire to work on what interests you, recognition, success, wealth, achievement, freedom, and ambition. This is not mutually exclusive with your desire to have a positive impact in the world through your company. It is just a matter of what came first.
The personal reasons outlined above are not wrong or bad, in and of themselves — so long as you don’t act unethically in their pursuit.
Companies that solve a problem (regardless of what motivated the founders) generally create net good in the world. But in the spirit of honesty, recognizing what motivated you in the first place could only help.