User replacable batteries mean more e-waste, not less.
The old school swappable batteries had batteries that died in negligible time and had to be discarded regularly, mechanical failure on the mounting bracket/clips to support the battery swap on the other hand send the device to the trash because they can't be fixed.
In addition to extra waste with every battery, and smaller batteries that have a shorter usefully life, replaceable batteries mean a weaker phone that is more prone to breakage.
What kills phones these days is not the battery or screen dying, it's the phone ceasing to get software updates. If you want to reduce e-waste, you should have legislation that requires manufacturers to provide full software support for say 5 years of major OS updates, and another 2-5 years of security updates after that.
Moreover even when people do replace a phone they tend to pass on the old one, not just throw it in the trash, but again, that's only possible if the phone is still usable.