I've liked all Sciamma's earlier films (particularly Tomboy), but couldn't get into this at all. I know it's a French period film, but I found it gratingly theatrical the way every conversation between the two seemed to be abstract and philosophical, and spoken at a very intense pitch. Almost like something from a Henry James ghost story. I was waiting for the moment where they would show some warmth towards each other, speak with some humour, say something personal, etc, as the relationship became romantic, but it didn't really come (I can only think of the bit where Marianne says she can tell when Heloise is hurt, or embarrassed, or nervous, by her tell-tale signs). Not being swept along, I found the ending a bit unearned - like Sciamma had thought of that final image first, then worked backwards. I thought About Schmidt or Birth did similar-ish scenes better. And Call Me By Your Name conveyed the feeling of falling love very well (I guess that's what I was expecting, and thought was missing).
Usual caveat: I might, of course, be judging it on unfair terms - repressed emotions and desires are a key theme. I was sort of hoping it was going in a Rosemary's Baby direction at one point too.
Also I was surrounded by people who weren't wearing face-masks (in East Asia, no less) and one kept coughing, so I was a bit distracted by the cunt.