>You are welcome to do it for free. The entire point of an UI library is to save time.. you can technically build anything you want for free if you don't value your time.

the comment seems more about how lousy the product it is, and sure I wouldn't want to spend my time making a lousy product, but if in my technical evaluation something sucks then there is generally a good chance that I can build something better.

So the comparison is between using money to buy something bad or using time to build something good and the phrasing would be something like:

You are welcome to use your time to build something that doesn't have all these problems.