There's plenty of devices that are still (with some effort) repairable. And there's plenty of consumers who take repairability into account when purchasing, like me and probably yourself after your experience with the A50. Also it's difficult, but the A50 is certainly repairable: https://www.ifixit.com/Device/Samsung_Galaxy_A50
Couldn't they just use a standard USB micro interface or Qi standard charger?
I have not purchased a Samsung device since.
But this is only because people have no choice but to buy unrepairable fridges and phones. If people could buy repairable ones then that would factor into brand reputation and people would buy the fridge or phone that's got 3% lesser specs for the same price for the peace of mind that being able to repair it in the future brings.
I have taken my A50 to Samsung, and they are not fixing it no matter how much I pay them. On my Withings smartwatch the glass cracked, and was considered under warranty. They explicitly told me it is unrepairable, and replaced the watch with a new one! How the Fk are they unable to replace glass on a watch?
Just about everything has already became either unrepairable, or uneconomic to repair, from fridges to TVs to phones to smartwatches. The are a few exception like vehicles or large equipment, but the events so far indicate that people will buy unrepairable equipment because they have already done so in many industries. Consumers generally have no way to know how repairable something is, especially for a new product.
Lastly, a device does not have to be completely unrepairable - it could require absurdly specialised and expensive equipment, that only the OEM will ever afford, so you will be back at the monopoly problem.