This is my "Hot Take" for the front-end world. I truly think modals are bad. Bad for the end user, and a crutch that too many developers and UX folk rely on.
Let's start with the users because they matter most. We have implemented modals to take over the whole screen, to be an interruption, and to hide all content behind it. My challenge for the experience is: replace every modal you have in your application with a browser dialog() call. The only difference is that the dialog locks the main thread—but you've already locked the thread in the users mind, so you might as well.
There have been numerous times where I need other data on the screen in the modal. But I can't see it, its hidden behind the modal. And I can't get to it. And of course, once you close a modal, whatever you did in there is gone.
Looking at modals on mobile is the nail in the coffin. Due to the screen size it must take up the entire screen. What is the difference between that and "navigating to a new page" in the mobile UI metaphor? When you actually navigate to a new screen you get the standard back button right where you expect it, right where it is like every, single, other, application. By using a modal on mobile you've confused your user and broken the standard UI metaphor for these devices.
Using modals is how we developers show our laziness. It is a crutch both in terms of not wanting to do more work in creating new pages (or states), and not wanting to think about how to improve the UI so a modal window is unnecessary. There are lots of possibilities that range from small and unobtrusive like inline editing, or more fundamental like left/right pane splits (e.g. a list on the left, detail on the right). I think we really need to start thinking about task-specific UX where we optimize for what task a user is trying to do. Build a UI specifically for that task. Don't just throw a modal into the mix because it allows the user to do something. I am willing to bet it is clunky. And if you had the job to use that modal window hundreds of times a day, you would quickly redesign it for something better.
I think the web would be much improved if ad blockers could block every custom modal window. Add modals to the deny list. There is an up-and-coming HTML <dialog> element, which is a replacement for dialog(). Let's build toward that, and destroy custom modals. I know people will abuse the dialog to take over the whole window—but it does not have to. And, if it is an HTML element it can be controlled by the browser; there can be system settings to protect users when we developers abuse it. I imagine the possibilities of site-lists that block their use of the element.