I remember thinking the same thing about 25 years ago when all the blues greats were dying off.
Really sad for me as I grew up with the Allman Brothers. Live at the Fillmore was my brother's favorite record and we listened to it A LOT. When I first started to listen to it I liked it, but I kind of dismissed them as being just another "white guys playing blues" band. The more I listened to it the more I liked it. Soon it became our gateway drug to Jazz.
I'd have to say, now it is among my favorite albums of all time.