The Magic Initiate feat states:

Choose a class: bard, cleric, druid, sorcerer, warlock, or wizard. You learn two cantrips of your choice from that class's list.
In addition, choose one 1st level spell from the same list. You learn that spell and can cast it at its lowest level. Once you cast it, you must finish a long rest before you can cast it again using this feat.
Your spellcasting ability for these spells depends on the class you chose: Charisma for bard, sorcerer, or warlock; Wisdom for cleric or druid; or Intelligence for wizard.

I realized that this does not allow you to take spells from the Paladin or Ranger classes (they also do not have cantrips, so perhaps that is the reason). But I was wondering if this change would be imbalancing:

Choose a class: bard, cleric, druid, paladin, ranger, sorcerer, warlock, or wizard. You either learn two cantrips and a 1st level spell or two 1st level spells from that class's list.
You learn any 1st level spells chosen and can cast them at their lowest level. Once you cast one, you must finish a long rest before you can cast the same one again using this feat.
Your spellcasting ability for these spells depends on the class you chose: Charisma for bard, paladin, sorcerer, or warlock; Wisdom for cleric, druid or ranger; or Intelligence for wizard.

It allows two new options:

1. You can take an additional 1st level spell instead of the two cantrips.
2. You can choose the Paladin and Ranger classes (getting two 1st level spells).

The Magic Initiate feat states:

Choose a class: bard, cleric, druid, sorcerer, warlock, or wizard. You learn two cantrips of your choice from that class's list.
In addition, choose one 1st level spell from the same list. You learn that spell and can cast it at its lowest level. Once you cast it, you must finish a long rest before you can cast it again using this feat.
Your spellcasting ability for these spells depends on the class you chose: Charisma for bard, sorcerer, or warlock; Wisdom for cleric or druid; or Intelligence for wizard.

I realized that this does not allow you to take spells from the Paladin or Ranger classes (they also do not have cantrips, so perhaps that is the reason). But I was wondering if this change would be imbalancing:

Choose a class: bard, cleric, druid, paladin, ranger, sorcerer, warlock, or wizard. You either learn two cantrips and a 1st level spell or two 1st level spells from that class's list.
You learn any 1st level spells chosen and can cast them at their lowest level. Once you cast one, you must finish a long rest before you can cast the same one again using this feat.
Your spellcasting ability for these spells depends on the class you chose: Charisma for bard, paladin, sorcerer, or warlock; Wisdom for cleric, druid or ranger; or Intelligence for wizard.

This change allows for two new options:

1. You can take an additional 1st level spell instead of the two cantrips.
2. You can choose the Paladin and Ranger classes (getting two 1st level spells).