Its probably spider mites. Look for webbing and small black spots on the underside of the leaves.

"it gets light and everything! "

How much light? Is it in a western/eastern etc. exposure?

If it is spider mites, I've seen other gardenwebbers recommend a mixture of 50/50 rubbing alcohol (isopropyl) mixed with water.

You can just use some bayer 3 in 1 on it to control the infestation.

As others have mentioned, spider mites are an ongoing challenge with English ivy. I have managed to keep about 7 ivy plants alive indoors. Though I have found spider mites on a few leaves, and there are probably a few plants that have some mites right now, I think the most important thing is early intervention. I don't think you should obsess over eradicating mites from these plants entirely, as they tend to come back quickly, but the goal should be to keep them under control in the first place. That being said:

1. Remove any infested leaves with a mottled appearance immediately. I see you have some relatively healthy leaves left, and you could keep those in tact and perhaps save part of your plant, but cut off the others.

2. Every time you water the plant (because I have a chunky soil, it's about once a week), gently spray the leaves with a shower or sink spray attachment. Turn them over as you spray them, feel the texture of the leaves over your fingers, examine them, and remove anything that looks discolored.

3. Some here recommend an insecticide, and I think that's fine, but in my
experience, you just have to be diligent in observing the plant more
than anything, before things get out of control.

4. Avoid transferring indoor plants outside in the summer. This is just a personal preference, as I don't want to have to deal with a bug issue once I bring them back inside or infest my other plants.

5. Ivy likes medium-high light, but also likes cool evenings, but also likes humidity so their leaves don't dry out. Can you say, "Goldilocks plant?" It's a challenge with most home environments as we tend to regulate temperature more moderately.

Ivy is beautiful, and it can be fussy, and I am by no means an ivy expert, and I have lost a few. However, having learned over time, I think the extra work is certainly worth it! Don't give up!

It’s because you keep the soil moist, wait until the top inch of soil is dry before watering again

No, it was NOT due to watering! The reason the ivy was dying five and half years ago was due to spider mites. As was explained several times previously, they are inevitable when trying to grow English ivy indoors.