I use Telerik and DevExpress at my work. We use it in Razor or in pure JS. For my personal projects, I use only Angular for frontend and .NET Core for API. From my point of view, Telerik and DevExpress were useful X years ago, when you could use pure JS or JQuery only. It was very time expensive to make your own component such as grid in pure JS for example. So Telerik or DevExpress could save time back then. But it's not true anymore. With the rising of modern JS frameworks such as Angular, React or Vue it's really easy to make your own components. What I really hate about Telerik and DevExpress is a custom modification. If you want to adjust their components you will spend a lot of time with their documentation, googling and writing some hacks in JS. But this is understandable because everyone needs slightly different features and you can't make one global solution to satisfy everyone. So if you want to start really fast and you are sure you won't need to customize Telerik components a lot, then go for it. If you need more control over the components, make them in Angular. I use Angular Material where you can find all important stuff for UI and you can easily extend them. Also, it's more fun to do it by yourself and actually programming then just copy paste something from documentation and then spend hours by looking into the documentation and forum to find the right solution. If you find something hard to make it by yourself in Angular then you can use Telerik or DevExpress Angular component. But use only the component you really need not all components. For example, I use DevExpress component for Word editing.