Should have played a Strat? Yes. Absolutely. That's what he does.
If you want to hear all that music played on the original gear, then go spin one of the albums or watch one of the many videos available.
If you want to hear what these players have evolved into, and hear them play their old music in that vein, then listen to the excellent recordings/videos of what they did more recently. Take it as served.
Isn't it a little odd to have a famous group play something, and then be told by others how they should have done it?
You know, when people go see Paul McCartney, they like seeing the Hofner. It's a visual cue that has incalculable value and meaning.
Nobody is suggesting how Clapton should have played. Rather, they are saying they'd like a closer approximation in sound to the band that is being advertised, and they'd like to see some of the really cool old gear, which, for many, adds to the authenticity of the experience. What Cream fan wouldn't want to see Clapton play The Fool?