The number of devs I hear complaining about "but but but... I want my webforms!" when confronted with "use a client-side JS tool with REST/AJAX/etc" is staggering. How do they think the rest of the world works?

Adopting these 'new fangled' approaches will increase their ability to move between worlds - perhaps even leaving the .NET compound from time to time. And perhaps more importantly, it will make it easier for people already skilled in front-end JS to contribute more effectively on otherwise-.NET-only teams.

You will almost never find top-notch JS talent (freelance or full-time) who also know how to interop with webforms and older ASP.NET tech. Widen the pool, by changing your practices, and you'll be able to compete more effectively.