If it uses spell slots to power, it should be a spell. Simple.
"COMBAT WILD SHAPE
When you choose this circle at 2nd level, you gain the ability to use Wild Shape on your turn as a bonus action, rather than as an action.
Additionally, while you are transformed by Wild Shape,
you can use a bonus action to expend one spell slot to regain 1d8 hit points per level of the spell slot expended"
"PRIMEVAL AWARENESS
Beginning at 3rd level, you can use your action and
expend one ranger spell slot to focus your awareness on the region around you..."
"FLEXIBLE CASTING
You can use your sorcery points to gain additional spell slots,
or sacrifice spell slots to gain additional sorcery points."
"ELDRITCH SMITE
Prerequisite: 5th level, Pact of the Blade feature Once per turn when you hit a creature with your pact weapon,
you can expend a warlock spell slot to deal an extra 1d8 force damage to the target, plus another 1d8 per level of the spell slot, and you can knock the target prone if it is Huge or smaller."
"UNIVERSAL SPEECH
6th-level College of Eloquence feature You have gained the ability to make your speech intelligible to any creature. As an action, choose one or more creatures within 60 feet of you, up to a number equal to your Charisma modifier (minimum of one creature). The
chosen creatures can magically understand you, regardless of the language you speak, for 1 hour. Once you use this feature, you can't use it again until you finish a long rest,
unless you expend a spell slot to use it again."
"LIVING LEGEND
20th- level Oath of Glory feature You can empower yourself with the legends-whether true or exaggerated-of your great deeds. As a bonus action, you gain the following benefits for 1 minute:...
Once you use this feature, you can't use it again until you finish a long rest,
unless you expend a 5th-level spell slot to use it again."
"SONG OF DEFENSE
Beginning at 10th level, you can direct your magic to absorb damage while your Bladesong is active. When you take damage, you can use your reaction
to expend one spell slot and reduce that damage to you by an amount equal to five times the spell slot's level."
"EXPERIM ENTAL ELIXIR
3rd-level Alchemist feature
You can create additional experimental elixirs
by expending a spell slot of 1st level or higher for each one."
(More such abilities.)
How many of these are now spells?