Honestly, I would be very tempted by appliances/cars that said "we've been using these parts for 20 years, and expect to do so forever so replacement parts won't be an issue". I believe some European car makers did that very thing.
Yes, it won't have certain definitions of "better", but repairability is a feature.
Give me a datsun sunny with standardized injerctors and a catalytic converter, then keep making the same thing with the same frame with a drop in standard 100hp electric motor and however many 12V 200Ah drop in lithium batteries I want to carry. If it's unsafe, add a roll cage, and a 5 point harness. If it's still unsafe lower speed limits, design better roads, and only let people who are highly trained drive.
Or a 250cc twin motorbike with 15 hp that weighs 110kg
Or a raileigh pusbike with a 3 speed sun gearbox, drum brakes and a brazed chromolly frame that will still be working after a carbon frame has turned to shards from UV or an alu or hi ten frame is cracked due to corrosion and work hardening and on its 10th drivetrain.
Or the same kettle or toaster or microwave that's been made for decades with simple dials and switches but without changing the shape for no reason or a byzantine menu to reverse engineer back to power and time (the only things that mattere and the interface often used in the 50s).
Make TVs a simple display with a standard mounting point for a standard power supply and a general purpose computer.
With spare parts, you have to keep the machinery and the knowledge to produce spare parts around for a X years, or make sure your parts won’t degrade for X years, predict how many you’ll need, produce them up-front, and pay for storage.
That worked reasonably well when machines had fairly standard replacement parts. If your part doesn’t change for years, keeping manufacturing knowledge is almost free, and predicting the number of parts needed easier because of the law of large numbers (if you sell ten variants of a design, you may know you’ll need 100,000 ± 10,000 replacement widgets, but for each part that may mean 10,000 ± 5,000, so you’d have to stock 10 × 15,000, knowing you likely won’t need 40,000 of them)
However, current hardware production is very flexible. Making a part slightly different to slightly improve a design is doable (examples in electronics: ASICS, custom battery sizes, custom LCD panels). Do that ten times in a single design, and the resulting device is significantly better.
I think this kind of regulation will trigger a lot of innovation in hardware manufacturing, and may still lead to products that are (slightly) worse if you ignore repairability.