Hello, yotaco_22. Azaleas get leggy when they do not receive enough sun. To promote fuller growth, you pinch the leaf buds as they begin to unfurl in early Spring. This is called pinching.

Be careful when doing this work around the bushes. Azalea roots are very tiny and fibruous. They reside in the top 4" of the soil and do not like to be disturbed. Adventitious growth cells along the stems will be triggered to grow by pinching and result in a fuller bush. Start this next year; you will need to do it for maybe 2-3 years.

The oak leaves are ok as long as they are not too too packed. I did not get a good understanding of how much the oak leaves are packed but, to give you a point of reference, azaleas should be mulched with 3-4" of any acidic type of mulch. They feed off the decomposing mulch so check the amount of mulch in Spring and Fall.

If the azaleas do not get much sun (aim for 3 hours of morning sun), consider raising the canopy of the oak tree a little, transplanting, etc. Indirect sunlight reflected off other surfaces like cement does count so see what works in your garden.

Luis