It’s better to translate the UI of a software when the feature design is stable. Otherwise every time you change the menu, you have to change 10 translations.

English is the most widely used language. If we can’t even capture a large number of English users, we fail. 

 Sure, but also internationalizing your UI so that localization can happen at anytime is even better. We can capture English speaking users and still cater to non-English speakers. I don’t think any of this is mutually exclusive.