If it's really "by design" then you are saying they have a staff of web developers who are told, "No, no, no... all that quality work you're capable of--don't do it. Here are some JIRA tickets to make the web site shitty and slow and eat the user's battery. Go implement them and make everything worse!"

What kind of sad, self-loathing software developer sits down and says "OK boss, whatever you say, boss, gonna go make it bad now..." I mean, I know to a lot of people, it's just a 9-5 and you do what your boss says, and "pride in your work" is not really a thing anymore, but come on. Who gets even a shred of satisfaction doing this?

I think a better explanation is just incompetence.