I have a few areas around my house that were originally planted with different shrubs to "fill the space"

Now that the shrubs have grown they abut one another. See attached pictures of an azalea abutting a Holly

and another azalea between 2 boxwoods. All of the shrubs are very healthy. Should I separate the azalea

from the Holly? Should I remove the azalea between the boxwoods so as to fill the space with the boxwoods?

You definitely have got some tricky situations there. I'll give my 2 cents…

Photo 1 it's hard to understand the larger situation there. The simplest solution might be to try some strategic pruning of both the holly and the azalea to see if you can make it look good enough and avoid major changes…

The easiest situation probably is photo 2. Matter of personal preference and the look you are going for, but I'd trim back the boxwood to help the azalea stand out a bit more as a feature. A 6" gap on both sides would be OK. When doing a fairly hard prune like that the pruned area might look pretty bad for a year until new growth comes in. Therefore would make sense to cut back an additional 4-6" to allow for that new growth (so if going for a 6" gap, prune back 10-12").

Photo 3 is a pickle of a situation. The holly is being blocked out by the large azalea. The holly looks pretty bad in my opinion, and my preference would be to remove it (might be quite difficult because of what is probably a large root system). The problem is the azalea is so big you'd need to replace the holly with something big. So if you want to leave the azaleas in place you could try replacing the holly with 2 large dark-leaved rhodos, or some other shade-tolerant shrub. But need to buy large plants (like 5-7 gal) that already have a nice full shape otherwise small ones would just grow scrawny reaching for the sun.

The azalea is so big you most likely can't prune it down enough to make an ideal situation for a smaller holly replacement. Completely re-doing that corner would give you lots of options to make that area look really sharp by adding a combination of new shrubs and perennials. But then you are pulling out both the azalea and the holly which is a lot of work. If it is a high-visibility area it might be worth it.