Way too slow compared to last version.

It takes nearly twenty minutes to load startup, a new world, and an existing world all on lowest video settings. Frame rate is a nightmare. And just version 1.13 is so much smoother, so the difference for versions is awful. Is there any way to refine this? I prefer version 1.12 because it runs the smoothest for a newer version, but I want to buy Realms to play with some friends on Discord, and I need to have the latest version to be able to do that. But I don't want to pay for a subscription if it takes almost an hour just to get the world to open, and then suffer through lag spikes and low frame rate. Will Realms ever be open for older versions in case other people have this problem, because personally I think it should, people are paying for the subscription, and I know lots of people that don't care much for the latest versions. And so far, the latest release is still acting like a snapshot for me