Because the subject of the sentence is tu capacidad, not tú.
Even though the sentence is about your ability, the grammatical subject is still ability, which is singular.
Crece is the third-person singular present indicative form of crecer.
A quick present-tense pattern:
Here, it matches capacidad, which is singular, so crece is the right form.
A useful detail: crecer is only irregular in the yo form (crezco). In crece, it behaves regularly.
Spanish often uses the definite article with abstract nouns and general concepts more than English does.
So con la experiencia sounds natural in Spanish, even though English often just says with experience.
This does not necessarily mean one specific experience. It can refer to experience in a general sense.
Con literally means with, but here it shows a relationship like as experience comes or through having experience.
So crece con la experiencia suggests that growth happens along with experience.
Other prepositions would change the nuance:
In this sentence, con is the most natural choice.
It can mean both, depending on context.
In this sentence, capacidad is closer to:
It sounds broader and more general than a specific skill.
So this sentence is talking about your overall ability growing through experience.
Because the sentence treats ability as one general quality.
Tu capacidad means your ability/capacity as a whole.
If you used the plural, tus capacidades, the meaning would shift slightly to your abilities/capacities as multiple separate things.
Both are possible in Spanish, but the singular sounds more general and abstract here.
Yes, you could, but it changes the nuance a little.
So capacidad sounds broader, while habilidad can sound more like a learned skill.
The original sentence feels more general and natural if the idea is overall growth.
Yes. Spanish word order is flexible.
Both are correct. The second version puts more emphasis on con la experiencia.
The original order is neutral and very natural.
The singular experiencia refers to experience as a general concept.
So:
If you say las experiencias, you are thinking of separate individual experiences:
The singular is more natural when talking about experience in a broad, abstract way.
In most of Latin America, crece is pronounced roughly like KREH-seh.
A few pronunciation notes:
So the full sentence is approximately:
too kah-pah-see-DAHD KREH-seh kon lah eks-peh-ree-EN-see-ah
Not if you want to keep the meaning your ability.
Without tu, the sentence becomes more general and no longer directly refers to your ability.