Reasons many devices are not repairable include: DRM built into parts to prevent replacements, no repair manuals (see Thinkpads compared to macbooks). Also measures to prevent people from flashing the firmware or updating the software once a company decides to drop support despite the hardware being still functional, or easy to put back up to speed by changing a battery.
Forcing companies to stop these anti-consumer strategies has 0 impact on the designs while making electronics far more repairable.
I find the "right to repair will make my devices big and ugly and appeasing to the evil tinkerers and hackers" angle really dishonest.
Even given that, I don’t see how “end users must be able to change batteries in a practical way” would not negatively impact the quality of the iPhone I’m holding in my hand right now.
From a water-resistance standpoint alone, I think my phone would suffer in at least one dimension that matters to me. (It’s an Xs Max and yes, I bought used, confident that the water resistance was intact. If I sold it now, the next buyer has that same assurance.) Phones get wet at some low (but not insignificant) rate; it’s hard to avoid that across the entire population.
One is the availability of original spare parts like screens and backside covers (aka the stuff that breaks very often) for ordinary people and repair centers. A phone that's glued together and absolutely waterproof as a result can still be called "repairable" under that definition as long as there is non-discriminatory (aka external customers get charged the same as manufacturer repair centers) access to spare parts.
Another is the accessibility of repair without special tools (cough Pentalobe) or the need to discard a fully functional component to access a defective one, e.g. when the screen is to be replaced you need to remove the glued in back cover first, a step that risks permanently damaging it by bending or breaking it. Most waterproof designs have a really hard time here as it's hard to make a waterproof design that is still easily disassemblable and slim/optically pleasing.
The third definition of repairable is if an end-user can replace a common wear item on their own: batteries most obviously, but also outward-facing connectors for headsets and charging/USB.
The fourth definition of repairable is the firmware side - aka, can people repair defects in the firmware like security flaws on their own after the manufacturer has ceased support, without risking to lose functionality. Apple is the worst offender of them all with not allowing "rooting" at all, but in most of the Android world the situation isn't much better - root your device and you'll lose KnoxGuard/TrustZone functionality (sometimes breaking apps relying on it, half the apps on my rooted Samsung don't do fingerprint auth anymore since rooting), and SafetyNet attestation will also fail, leading to apps either stopping to work entirely (banking apps, just f..k off, I know what I'm doing) or offering reduced functionality (Netflix).
And with all of the various definitions of repairability in mind, you will always have some trade-offs to make.
