Well it’s fine, as addon are there to improve blender for a particular task.
It goes the same way with 3D models that you can get, is it considered cheating if you made a scene that uses only megascan assets for instance ? https://quixel.com/megascans/
Well it mostly depends on the context and how you put it. If you claim that you modeled all these object then it’s a fraud…
But , maybe your interest is more on image composition, lighting or storytelling then it might seem logical that you don’t want to bother with modeling asset and using megascan makes sense.
Finally, it also depends on what you want to be in CG. As a professional looking for work in a studio it’s more valuable to demonstrate that you can model or scan stuff by yourself even if the result is less good than if you used pre-made assets. There also it depends on what position you’re after.
In that context a piece that you present should give the most information about your abilities and what you’d like to do in CG.
Now if you do CG for fun, you can use whatever tool, assets, model or else you want as the main goal is to have fun…
Finally cheating in CG carries a double meaning, it can be used to describe a fraud, but it’s also describing a skill that is about cutting corners. If a tool allow you to do the same thing in a fraction of the time then it’s not about cheating , it’s about efficiency. In the meantime we are cheating all the time, if a photo can be used as background rather than doing it full CG it’s probably the way to go and it would be pointless to model the background if this doesn’t bring other value than “I did everything”…
If you want to add textures to your models, it’s better to first look at ambiant.cg and download a few of them, rather than going out with your camera and make your own textures, unless you are really interested in building textures and you want to study that more closely.
Once you acknowledge that to be good at CG you need to put a lot of time and effort, it’s ok to use whatever you need to make progress, and the time you don’t spend doing something is some time that you can invest in what really matters to you…