[paranoidrobot]

I would much rather they served the same content with 'responsive' designs, than do browser-sniffing and serve me a mobile page.

More often than not, I immediately go and switch out of Mobile site for pretty much everything I visit on mobile.

Features are missing, functionality is broken or gone, they force text/page sizes that don't work for me and block zooming (Firefox thankfully allows me to override that b.s now), and they serve "Install our App!" overlays.

Doordash I found is like this - some stores use them for white-labelled Delivery and SMS/Email you a link to the tracking page for your order.

I click the link on my desktop, I get a standard page, it shows a tracking map.

I click the link on my phone, I get a mobile version of the page which does have a tracking map, but the entire screen is covered with an overlay that says "Install our App!" with no dismiss option and you have to try to make out the driver's location through the 80% opaque overlay.