I’m happy to use Bladesinger as an ancient Gnomish tradition in a world that doesn’t even have the Seldarine. Arcane Tricksters are a derivative form. Elves of this world tend more toward Eldritch Knights.
And that's an
absolutely good and thing!
For your world.
But retconning the lore of the
Bladesinger as being something open to all races by default, rather than the special racial champions of the Elves, means that some players will come to the table
expecting to be able to play, say, a Dwarven
Bladesinger, and will feel resentful if the DM tells them that his
Bladesingers are the original, special, semi-legendary Elf-only racial champions.
I have seen this sort of thing happen more than once with players wanting to play Dragonborn in my brother's campaign, which is in a world that
has no Dragonborn as he despises the gaudiness of the race, and the players became resentful and sullen because they weren't allowed to play the race since it was included in the PHB, even though the DM explained that he does not like the race at all and that dragonpeople do not fit with the style and themes of his world. As I have said before, I despise the Dragonborn, but if they had been included in the DMG as an optional race which DMs could choose to include I would have been fine with it, but instead they chose to include them right in the PHB, making this new race suddenly as common as Gnomes (!!!) and all-but forcing DMs to shoe-horn them into their worlds.
The DM's note provided in the SCAG was fine, explaining that by default the role of
Bladesingers was restricted to Elves only as the champions of the Elven people, but that DMs could alter that fact for their own campaigns if they so chose, and it should have been left at that.
This idea of removing any and all racial restrictions on important cultural roles is just a
horrible idea, and only serves to take away flavor and render worlds more flat and lifeless (one could even go so far as to label it cultural appropriation of an extremely important and unique Elven cultural role, and I could easily envision the Elves going to war against the thieves of this sacred Elven tradition.) Bladesingers weren't just one more type of Wizard...
they were the elite champions of the Elven people! But now they've been reduced to just another run-of-the-mill variant of Wizard that uses swords. Its rarity, specialness, and meaning has been totally stripped away. And that is nothing but a
loss.