This is a super simple mod I whipped up to fix a problem I've been having, and figured others might find useful.
By default in Minecraft, when you assign a modifier (ctrl, shift or alt) to a keybind, it will still call the base key. For example:
This would never happen in real controls but it's a good way to show the problem. Here, if I were to press D, I'd strafe right as normal. However, if I press Ctrl+D, the game interprets both strafe left AND strafe right, does them both at the same time, and therefore I don't move at all. This mod overrides that behaviour; if a modifier key is being pressed and is required, it'll ignore the unmodified behaviour. You can now strafe left with ctrl+D while strafing right with D! If a modifier is being pressed and there is no valid keybind for it, then everything is ignored and works as normal.
Please note, the keys will still show as a clash in the key menu. This would be a bit more difficult to fix and isn't a huge problem, I recommend using a key management mod like Keyboard Wizard to help with that.