It may seem absurd that the apps is costing Kroger that much but my family's experience backs it up.
In the post-COVID era, my wife has become quite accustomed to digital shopping. We actually live closer to a Meijer, which is basically the Midwest's answer to Walmart, except it's decades older. (You may be able to thank Meijer for Super Walmarts; it's Meijer that proved out the concept of attaching a grocery store to a general superstore for Walmart, and it gave Walmart some difficulty penetrating in to the Midwest so they had to add it to compete.) Of course COVID caused a big app rush and at first everybody's app was pretty crappy, so we just stuck with the closest one.
Over time, Meijer's app slowed down pretty badly, so my wife ended up switching to Kroger. I saw a lot of Kroger bags. One of the biggest problems with the Meijer was that trying to add a second of any item was a synchronous round-trip to a rather busy and slow server, so goodness help you if you wanted, say, 6 bananas. Going from 1 to 6 could literally take 30 seconds on the worst days. And that was just the worst issue, the whole app was generally slow and prone to failure.
But somewhere around two years ago, clearly someone at Meijer got the performance religion and cleaned up their app and website. I still wouldn't call it blazing fast, but I would call it acceptable by modern standards, and it blew away the Kroger app of the time... again, not because it was pushing 120fps with super low latency, but just because it was fairly reasonable to use. Adding five more bananas is now just tapping the button five times, and while I can still kind of see the async requests chasing each other a bit, it pretty much always ends up converging on the correct number in a couple of seconds. So my wife switched back.
I don't know what Kroger's current performance is, because now that we don't have a problem we haven't been seeking solutions. So they've lost thousands of dollars of business over the years to Meijer from us.
An anecdote, of course, but I suspect a common one.
I put this out there in the hope that it will push more people into caring a bit more about performance. I think there's a fairly large range where "normal people" will use a sluggish app or website, and wander away, and if you do manage to rope them into a marketing survey they won't necessarily say it's because it's slow, you'll get other rationalizations, because it isn't a fully-conscious reaction and realization for them... but nevertheless, you'll have a very, very leaky funnel and just reading those surveys may not tell you why.