Thank you! Would you recommend filling the crack myself or just let it be and just watch it?

You could caulk it, but it still might open up a bit. This is very common when you have a concrete pour at two different times and they meet at an angle: there is often a bit of shrinkage and settling. It doesn't look serious to me as you don't actually have a crack in the foundation, but just where the two surfaces meet. I wouldn't worry about it as it doesn't appear to be structural.

What are you filling it with and what are you watching it do (rhetorical question)? This is not a huge problem in comparison to all the detail failures a house can have, but unfortunately these little things are never a simple 1 and done answer.

Your condenser pad has settled, maybe even a tilt towards the outside edge, and torqued against the cementious stucco that formed a connection to the slab. So, what you would be watching for is more settling causing a larger gap or more cracking of the stucco. If you have a wood foundation, water entry is a problem, pests for wood or concrete. But it appears a bigger issue predates the condenser pad settling and has exacerbated the problem - no matter the foundation type, not having a weep screed is not acceptable and having grade above the stucco is a moisture (and aesthetic staining) issue.

So you can caulk and watch. Or look around the house and see what else the stucco workmanship can lead to, evaluate warranty or cost vs long-term problems, and decide if more should be done or not, based on what you are comfortable with.

@kudzu9 Thank you! I really appreciate the advice.

@3onthetree Thank you so much! I really appreciate your advice on this!