Why not ? Lemar's not a like for like replacement for Santi anyway but some of the aspects of his game are similar, like having the ability to skip past players for fun but preferring to let the ball do the work for him or being press-resistant af as well as having the flexibility of mind to make a decisions ina split second when his first, second or even third pass have been closed down which can't be said for someone like Ramsey who more often than not just passes for the sake of passing as soon as his first option disappears which is a problem.
Back to Lemar though he's also said himself in the past "I am trying to avoid duels and concentrate on passing and movement as much as possible," and you can see it in his game.
I say that because Lemar's former trainer Philippe Tranchant who is also the man credited for his arrival in Caen (& the one who helped nurture Raphaël Guerreiro through Caens ranks too) has said in the past
"Thomas is a player who fits perfectly with the philosophy of Barça,"
"His left foot is a hand. There is Iniesta in him."
Don't get me wrong though if I had to choose from either Thomas Lemar or someone like Naby Keita I'd nab Naby all day mainly because there's nothing else like him on the market but that said if you can sign Lemar YOU SIGN Lemar.