Hi, @stroncea!
I’m not an expert either, but I think MNIST is a pretty ideal dataset.  I’m not “taken aback” that a fully connected network would perform well, so maybe it’s ok?
With that said, even though your network is “basic”, it actually has a lot of trainable parameters, and will likely be slower to train, have a larger than necessary memory footprint, and be more prone to overfitting than a network that includes convolutions.
–SEH