Oh boy, do you know that device manufacturers are actually refusing to repair plenty of devices - I am not talking about warranty shenanigans, but refusing to repair for any money at all:
https://www.youtube.com/watch?v=9-NU7yOSElEI 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.