The backwards compatibility is really a challenge, but I think more importantly dumping Knockout and Luma and all that insanity and going towards the Hyva route, or going more-headlessy with a good starter theme would encourage people enourmously.
Magento's frontend cluster-F is the reason we moved away from it. It was great to have such a good pricing engine, integrations pieces, currency support etc, but all of that skillset which is magento's core capability being a really well rounded online OMS is overshadowed by long and expensive turn arounds on frontend work.