Zardnaar
Legend
Yes and no.
I feel strongly, Custom Lineage must be a core player race option.
On the other hand, a SETTING can and normally will focus on a handful of specific races, and either deemphasize or ban all of the other races. This includes Custom Lineage. If the DM has a vision of a world setting that has specific races in mind, and assuming the players are enthusiastic about this setting, the DM can ban the Custom Lineages along with all of the other inappropriate races.
I am sensing a spirit of the times, players are increasingly inclusive and yet at the same time appreciate specialized settings.
Not every setting needs to be a kitchen-sink pastiche of Forgotten Realms!
People seem to like a focus but don't care to much what they are.
I find a new setting with a tight focus more interesting than anything goes.
Even something like Eberron built as anything goes still spotlights the 3 new races.