Having worked on what I would classify as a very large and complicated mobile/desktop web app for a few years now, I would probably choose a different direction if I had access to enough developers.

I'm fairly convinced at this point that with enough developers, the best approach is adaptive if you plan on building a web app with considerable complexity. Completely isolated development, fully custom design and code for mobile.

With an adaptive site you have the choice to include or exclude elements which may have a major performance impact on the app, including for instance: entire view/component trees, media queries, heavy JS like graphs or ads. You also get to make web-unfriendly decisions like using a custom renderer if you think it will produce a higher quality experience, like Flipboard's React Canvas from several years ago: https://engineering.flipboard.com/2015/02/mobile-web

Overall it's still very context dependent, but I would recommend for larger teams to not completely discount adaptive mobile sites if they're looking to build the highest quality mobile experiences.