I'm against any restrictions, it should be X race is not that great at being Y class, but never anything like they can't. It's something I'm glad that died in fire with 3e, and I don't think it should ever come back.
If there are restrictions it should be only up to individual DMs, and never even something to take up space in any book.
What are your views on racial and class restrictions not based on combinations?
Should dwarves be allowed to be fast?
Should wizards get healing magic?
Should halflings, gnomes, goblins, and kobolds be able to weld two handed medium weapons?
Should clerics be able to be proficient with non-maces by default?
Should arcanists be allowed to cast in armor?
Should halflings be allowed to wear shoes?
Should dwarves hate trees and be unable to use wooden items?