Why are there so many errors in w3c? And advice (themeforest, html)

Webflow often claimed that the generated webflow code is very clean and the sites created in webflow are loaded very quickly. But by inserting a webflow/ecommerce link in w3c - more than 100 errors were found. Why?

I wanted to create a webflow template to send for moderation themeforest, in the category html. But now, apparently, it is stupid to do? After all, the code does not pass the W3C check, unfortunately