I'm 110% in favor of a sidebar telling umpires that it won't ruin their game if they decide to shuffle those restrictions around for their homebrew settings, or toss them out entirely if their players don't want to play that way. Starting about '96 or '97, I started rewriting the whole race/class system before every campaign I ran.The downside, of course, is that building up racial concept in the setting via mechanics necessarily limits the amount of player expression to define the character and their image to their own taste. The balance of "player authority to define their character" compared to "the ability of the system to define the setting" is an aesthetic consideration that needs to be decided by the table.
It's a lot easier for an umpire to remove restrictions than to add them.
The principle behind the restrictions was solid; the implementation was terrible. The biggest and best tool that AD&D had for differentiating the multitudes of playable humanoid species... and 90% of them had the exact same options as Dwarf: Fighter, Cleric, Thief, Fighter/Cleric, Fighter/Thief. Goblinoids replaced Fighter/Cleric with Cleric/Thief. Mage of any kind was rare, subclasses of any group were rare. It was sad, and I'm pretty sure that's a big part of why people ignored them before 1999 and why they got thrown out.Having played in that era, I'll say the amount of stereotyping and redundancy that it created was not worth the trope reinforcement. If dwarves are typically LG, very religious and martial, why can't they be paladins? If halflings were nimble and rural, why not rangers? If elven art is considered peak, why are there no elf bards? Why can gnomes only learn magic if it's based on illusion? Etc etc.