And? What's wrong with your latter point? If anything, you should be more inclined to try a new web app that fits this bill. It means the developer is spending more time on getting the basic MVP up and running and isn't putting precious early-stage resources into pure aesthetics.
Try it out, see if you like it. Bootstrap is good enough - it's clean and straightforward - a totally reasonable "default" for the web. It says to me that the developer is savvy enough to know that Bootstrap exists, is perfectly fine for a V1 product, and that if we the users show the idea is good, they'll have plenty of money to put into a super-original design later on.
I think the issue with the UI can be traced down to his/her choice of using the default hero-unit on top, and the colors of the buttons. Change the color of the hero-unit so that the grey is not so obvious. Also, change the colors of the buttons from the default bootstrap blue to the lighter blue used in the nav bar on top or some other color that matches. The color of the primary button is just ugly.
I think that today, it communicates that you don't have too much appreciation for the final user experience, just want to test a concept.