Setting-wise, it irks me that a traditionally elven weapon is worthless to what are supposed to be elves dedicated to defending their kind. It is pretty worthless to most elves, actually.
Mechanics-wise, I know spellswords are in a pretty good place right now, so buffing them might seem like a silly idea, but the Bladesinger path is pretty firmly behind both pathless and abjurant champion spellswords, sacrificing plenty of power for no tangible benefit.
Contrary to the others, they are essentially stuck wearing elven chainmail, which kills build variety quite a bit. Same with the shield slot, which the other spellswords can use with a bronze shield that they can enchant with whatever bonuses they want. It pretty much kills equipment variety for the class, and it makes gearing significantly harder than it is for their peers.
The worst offender here would be the weapon choice. Bladesingers only get access to rapiers and longswords, and there is literally no reason to pick anything but the rapier. Enchanted bronze rapiers or Mdamask ones are the only viable choices here. Arelith has a tradition of creating some special weapons for the non-meta weapon types, and there is a longsword meant specifically for elves.
Yet, with the stats it has, there is literally no incentive to ever use the Elfblade over anything else. The rapier has more damage, more crits, and the same ab as the Elfblade when wielded by a Bladesinger. I guess it can be very rarely outclassed in some rare situations, but since imbuing a weapon is a once-per-rest thing, nobody will ever pick it over the rapier. And even if they did pick a longsword, using the MDamask one would probably work better than the Elfblade as well.
I'd propose to give Bladesingers some kind of synergy with the Elfblade, the same way they have with the Elven Chainmail. Be it higher AB, like making it +6 after imbuing, maybe adding some extra elemental damage.
Or maybe just buff the Elfblade for everyone, as the thing that used to be a pretty cool alternative to scimitars as one of the few +4 weapons, the thing generating RP for people trying to get it from the normally isolationist elves, is now overshadowed completely by all the new +4 unique weapons added to the crafting system.