In 5e, that's just how minor illusion works. It's a cantrip which can be cast at-will with the use of an action. If you want a glowing illusory sword without altering mechanics of minor illusion, there are leveled spells for that. Or you might come up with some other creative solution that would layer on a shimmering effect.Which read literally means I can't create a minor illusion of a glowing sword mounted on a wall, which seems a bit (as in, a lot!) over-restrictive.
I-as-caster also can't have the illusion react properly to light sources e.g. reflections off the shiny blade of a non-glowing illusory sword.