Lets say two people want to mow their lawns...
Person A uses a tractor, the results are amazing and everybody complements them.

Person B looks at the lawn and says, "I can do the same thing, but I'll use a weed wacker instead!"

The end result is the same, but person B used a vastly inferior tool to do the job. Someone comments, "I love your lawn, but I've seen this type of cut before!" Person B comments, "yeah, but did they do it with a weed wacker?"
Another example would be someone making a level where you are forced to jump from P switch to P switch, but they used the SMW theme (where you can accidentally pick up the P switches) because it looks nicer than SMB theme.

My point is: people generally only care about the end result. If you are going to limit your self using a inferior theme that's fine, I get the appeal of wanting the "challenge" of doing it, but I don't know why you would think someone would be more impressed using an inferior tool (theme) for the job.