Speed and uptime are also features. If customers like speed/uptime (they do) we need to make sure management prioritizes them and understands how certain features will work against speed/uptime.

been a juggling act for me for some time, and always comes down to - they'd rather take a performance hit vs. harm the branding/interactivity. tho we're in a very niche market that doesn't seem to mind (i do my best to make it as efficient as can be)

This.

We have a very slow eshop, worst than any competitor, yet the priority is always new features that will make the life of users even worse.

Cool-looking things appeal to customers, and also to developers.

It's a bit like your car. It takes you from place to place and could drive much faster than speed-limits or traffic-jams allow. But getting from place to place is not all you want. You want to pay extra for the coolest looking fastest wheels you can afford.

When you work with an app or app-development tool that looks cool your self-image improves. You are a cool dude because you work with a cool-looking application. Seriously, it does have an effect on me.