Ask HN: Is using Redux or React making a large app slow?

I know the title can sound clickbaity, but I have a personal practical question born from my observations.

As an independent developer I a build frontend applications for my clients. I have a set of tools, one of which is [1] Redux DevTools extension for Chrome.

Its window is often open while I am working.

What I noticed is some major large webapps keep it enabled in production what makes me think they at least use Redux, not necessarily React. I see actions dispatched in the Redux DevTools window while I am performing my tasks in these apps.

To name a few - Atlassian apps: Jira and Confluence, and Balsamiq.cloud mocking tool.

The other thing I saw is these are large and very slow and seem like devs just applied some common techniques and patterns from Redux world to their large apps without putting much thought into it.

So, I wonder (ignoring the price of implementation) would it be a better solution for a large app to be custom-made? Hand-made classes, dom-updating, data-fetching, event-dispatching layers.

Please share your experience if you have a related experience of migrating a large web application to React+Redux+Saga. Is it worth it to move the WHOLE app into this ecosystem or just parts of it?

Thanks.

[1] https://github.com/zalmoxisus/redux-devtools-extension