It’s a little hard to tell from the picture alone, so take my thoughts with a grain of salt, but it does appear to be etiolated. Direct sun (or what we think of as direct) might not be the issue necessarily. Sometimes consistent, lower levels of light can help maintain lower growth — for example, using a plant lamp for ~12 hours a day, pointed more specifically towards the base. A good rule of thumb is to hold your hand between the light source and the plant and check how “sharp” the shadow is. A sharp shadow means the light is strong, a fuzzy shadow means the light isn’t going to be as impactful. Aside from light, if the lower leaves are turning yellow and also mushy, or yellow and also crunchy, it could be a watering issue. And then there’s always plants who like to decompose their own leaves in an attempt to regain some energy reserves. Maintaining a diluted fertilizer schedule could help. Sometimes it’s hard to know where to start! But little adjustments over time is always a step.
I think it looks lovely. Something I like to do with vining plants is propagate the extra long vines and pot them back into the same pot. It’s a fun way to have more plant babies, more vines, and a fuller looking pot!