I've considered making hunter's mark and always known, not a spell but just an ability you trigger by using a spell slot. Otherwise it's just a tax, it's so mandatory; you likely only get 3 first level spells and there's so many good choices.
This frees up spells known for other purposes. Keeping it from being a spell also frees up concentration. Hunter's mark is just expected to just always be on, but it's competing with all the other good ranger offensive spells, like hail of thorns or ensnaring strike that are also concentration.