If rangers and bards didn’t have spell casting how effective would they be? Or if the spell casting abilities where lower they had less spells known and able to cast? Thanks 

If those charactes could not cast spells, they would be significantly less effective than they are now.

But how so? When I look at there class it seems spells are unnecessary, or at least don’t need as much. 

The ability to cast spells gives them options.

Taking away the ability to cast spells removes those options.

Removing options reduces a classes flexibility and thus makes them less effective in certain scenarios.

If you take anything away from a class, you will implicitly make it less effective than if it had that thing.

You would have to replace it for something else. Especially with Bard, spellcasting is integral to the class. As a Glamour Bard, in our last fight, my turns consisted of:

Action: Silence, Bonus Action: Mantle of Inspiration
Action: Blindness/Deafness, Bonus Action: Mantle of Inspiration
Action: Vicious Mockery, Bonus Action: None
Action: Blindness/Deafness, Bonus Action: Mantle of Inspiration
Action: Vicious Mockery, Bonus Action: None

A Bard's spells are about battlefield control and manipulation. If you take them away, then what are they left with? A basic shortbow attack? For Valor and Swords bards, its less important, since they will be attacking most turns, but not all, and some of their spells are bonus actions. For those subclasses, their spells usually fill the Exploration and Social Interaction pillars.

Quote from Lordneg >>

But how so? When I look at there class it seems spells are unnecessary, or at least don’t need as much. 

There's a bard in a campaign I'm DMing and she's a primary spellcaster, I can't remember the last time she did something as an action in combat that wasn't a spell.

Removing access to spells is removing a lot of powerful functionality.

For example, a bard is the best counterspeller and dispeller in the game, because of the Jack of All Trades feature. 

Quote from Lordneg >>

If rangers and bards didn’t have spell casting how effective would they be? Or if the spell casting abilities where lower they had less spells known and able to cast? Thanks 

Quote from Lordneg >>

But how so? When I look at there class it seems spells are unnecessary, or at least don’t need as much. 

I think the real questions are, "what do you hope to accomplish by taking those spells away" and "why do you think they are unnecessary"?

Bards and rangers have spells for a reason.  They have spells because of the legends from which the classes are based and the general role they fill.  The current bard is an alternative support caster with little to offer based solely on skills, inspiration, and combat potential in comparison to the other classes.  The ranger is meant to fill a similar role compared to the druid as the paladin to the cleric.  They are designed to have spells so taking spells away will have a large impact.

The UA: Class Variants is giving more spells to the ranger, not less.  ;)

Saying a ranger doesn't need spells would imply that a paladin does not either for the same reason.  Saying a bard doesn't need spells would imply that a cleric or druid doesn't for the same reason.  Cleric's get channel divinity and druids get wildshape.  Bards get skills and inspiration instead.  Bards only get 3 subclass features compared to other classes 4 and a lot of the entries on the class table are just scaling lower level abilities up a bit.

A bard with no spells is left with bardic inspiration, song of rest, jack-of-all-trades, expertise, counter charm, and a limited number of college options.  Light armor and a couple of weapon proficiencies isn't going to carry them through much at that point.  A ranger with no spells has a lot of situational class abilities based mostly on skill benefits and terrain.  A fighting style and extra attack with some subclass options isn't going to carry him far either.