It’s dark because it’s covered in sooty mould. That will be a result of an infestation of aphids or scale. Given that it’s a Euonymus I’d suspect scale. But there also appear to be cast off aphid skins on some of the leaves. The flies might be attracted by the mould but I’m not sure about that.

thanks for your reply! any suggested remedy?

Looks like a crape myrtle. Can't comment on "fly infestation" without being able to see what it consists of - some plants will just be places where flying insects like to sit. That said there is an infestation of some kind of sucking pest on the scene because the crape myrtle is covered in sooty mold fungus. This latter appears when a plant itself is infested with a sucking pest such as aphids that secretes excess sugars called honeydew. Or there is a taller plant nearby from which honeydew is dripping onto the plant being looked at. With the sooty mold having been growing on the deposited honey dew.

There are multiple issues going on here.

First, the shrub (which appears to be a camellia) is suffering from a whopping case of sooty mold. That is what is making the leaves dark. The sooty mold is not a terrifically serious issue itself - tends to be mostly cosmetic - but the causes behind it are worth investigating and correcting if possible.

Sooty mold is a fungus that grows on the honeydew or sweet, sticky excrement of sucking insects like aphids and scale. And they can be damaging to the health and vigor of whatever plant they can be found on. And sometimes they are not on the plant that develops the sooty mold but on overhanging or adjacent plantings. I don't really see anything in the photo that would qualify, so would assume the shrub itself is the source. However, since the SM takes some time to develop, the honeydew producing insects may or may not be present now.....I'd check anyway.

If no honeydew producing insects present - no sooty mold development. It can be washed off the foliage and that will immediately improve the shrub's appearance and help it to 'breath' easier :-) The flies are also attracted to the sweet substance.

I am not 100% certain but but it sure looks like a camellia. And they can be pruned relatively easily, typically right after the bloom cycle. How small you can be able to keep depends on the type or cultivar - some get a lot bigger than others. Offhand, it looks like a less than ideal choice for that tight siting without requiring at least annual pruning to keep size in check. I'd consider moving and replacing.

I thought I could see alternate foliage. Maybe not. Perhaps we can have some better picture in order to settle the id. Does it bloom? Are those old bloom stalks on the tips at the top?

yes it does bloom but don't think it happened too well this year...

I thought I could see alternate foliage

crape myrtle leaves

https://www.bing.com/images/search?q=crape%20myrtle%20leaves&qs=n&form=QBIR&sp=-1&pq=crape%20myrtle%20leaves&sc=8-19&cvid=4A9745F52A704982BAC4EFF9330E9133&first=1&scenario=ImageBasicHover

i would replace - we were thinking of an evergreen similar to the ones on the 2 sides that can possibly be shaped in a circular fashion for an aesthetic appeal? secondly, is planting of replacement recommended by professional only? and what is the suggested height of replacement tree at time of purchase?anything to avoid or be aware of if shaping the new bush on our own?

Just to be difficult I'll say it is a privet.

The sucking bugs making the honeydew (poop) that is attracting the flies and plenty other small wasps and such and that is providing a sugary medium for the black sooty mold to grow and cover the leaves has been well covered.

I don't think a round evergreen ball in that spot is the best idea. In fact that sounds like a bad idea. Which is why I'll go with it being the crepe myrtle that I really think it is. That is worth keeping and saving. Give it a drink of systemic poison to kill the sucking bugs and a bath. A crepe myrtle allowed to be a small tree will look much better there than a round green ball.

if we keep this tree, how careful do we have to be if trimming as not to kill it?

Having seen your other post about chopping the top off the arborvitae on the other side of the steps, the desire for a round green ball instead of a black buggy crepe myrtle in the middle and noting the two chairs on the porch, it is getting clear the bushes are blocking the view from your chair. Is this what the pruning questions are really all about?

Plant, building and design wise there are a great many years available to let the plants grow, to train the Crepe Myrtle into a real tree that reaches the second floor, all of which involves little to no effort on your part.

This is obviously a duplex. is it a condo? Do you own and maintain the land and bushes under discussion or is this about keeping the view from your chair unobstructed? Are you trying to find out how much you can chop off without killing the plant hoping nobody will notice?

I had a Eunoymus like this and it attracted flies like crazy when it bloomed. I ended up cutting it down because it grossed me out having all the flies. All the research I read said to cut off the blooms to keep the flies away. It didn’t help.

Its also a very messy shrub. It has runners and spreads everywhere and anywhere.

I think we’ve been persuaded that my id of Euonymus was premature. It’s since been settled that it’s a Crape Myrtle. Plus not all Euonymus have runners. There are shrub forms.