Giltonio_Santos
Hero
Creating brand new spells, according Level Up sensibilities, is also a way to be backward compatible. D&D 5e can easily import new spells.
I second this suggestion. Also, sometimes a new spell can go a long way to improve what seems to be a weak archetype. Look at the Beastmaster, for example: having a version of hunter's mark that you could cast on your beast would improve it a lot without the need to change the core ranger.