As others pointed out, your blazing spotlight of inexperience is the only reason you might be claiming that d&d is not "default" for ttrpgs with playable elves in core. There are other systems with elves in core like pathfinder shadowrun & so on... but even one of those doesn't change the more important part about the initial poor handling. The fact that your playing "you don't know what system I'm running, it could be important" is another tick in the inexperienced column. If it wasn't d&d or it was some ultra-obscure niche setting where it might matter rather than d&d or some d&d in all but name system you'd just name the sytem & people would agree if it needed more clarification all but outright confirms it.With this I agree. That's why I am so very confused by the vehement negative reaction many seem to have with me limiting playable races. If they are far from the most important thing on the character sheet, what does it matter if they are limited. After all, that still leaves all the things that are not the character's race.
It's ok that you made a newbie mistake as a newbie gm, it won't be your last The important part is that you learn from it, unfortunately for the long term health of your group it seems that you are insulted by any advice & take the very idea that there are things you could do better as an insult to your authoratah. People are saying you were wrong because instead of expending even the tiniest effort working with player4 to find out what about an elf interested them & redirecting that interest to one of the many things that do or could exist within your setting capable of wearing that interest of player4's towards the elf. Much like your choice to play the you don't know the system card without giving details your lack of detail in the player trying to work with cartman posing as cartman speaks volumes about your failings there.
It's ok to say x race is not accceptable & I'm sure there are several I refuse with the following house rule
- Allowed races: limited to those in Rising from the last war &those in exploring Eberron, the phb’s variant human is not allowed.
- Allowed backgrounds Oracle of war, Adventurer’s almanac, & if applicable ExE backgrounds.