In the previous century when web technologies were more primitive, modal dialogs were created in new browser windows. We all remember pop-ups and what a horrid experience that was. Developers (and spammers) abused this behavior so much that browsers now reflexively prevent pages from opening new windows in most cases.

I leave almost any site that interrupts me with a full screen modal dialog, especially if it's a prompt to subscribe to a newsletter. This abuse has become the norm. I have even seen desktop software adopting this behavior. A licensed copy of Guitar Pro 6 will interrupt you with a fullscreen ad for Guitar Pro 7. Unforgivable. Respect what the user is there for, and you might earn their business.

Edit: I recognize that there are some positive, responsible uses for this technique (extending forms/controls; search suggestions, assist the user rather than interrupt) and good examples are shown here. Please excuse the Sunday rant.