It's such a terrible language we spent the last 2 decades fixing its warts, adding one layer on top of the other. And now you have es7 + typescript + jsx + some magic introspection + code splitting + weird non standard imports, all that turned into regular JS and source maps, in a complex concurrent and async env that deals with graphics AND the network, 2 of the hardest things to get right. All that with zero stdlib, multiple incompatible clients, specific extensions for each store/router/event system you use and hot reload live pushing code.
And you wonder why it's hard to debug ?
I get that tooling is supposed to make our life easier, but let's be nice with the poor guys that have to work on the monster that must be usable with that stack.