For girls, the vast majority of popular names will date to some extent as technically there are very few have proved completely timeless (Elizabeth and maybe Maria? - even names like Alice, Eleanor, Charlotte, Emily, Anna, Rose etc have sometimes dropped out of the Top 100 ranks historically over the years).
And while I do really love a classic name as a “timeless” feel is particularly important to me personally (well as much as you can get for girls), it doesn’t seem to matter for a lot of people - and it doesn’t sound like you have a particular classic name in mind? More like that while you love the name you chose, you are worried it’s too popular? And so that has focused your worries about the name.
I wouldn’t worry about the popularity aspect at all - imo a popular name has far more pros then cons (unless your surname is super popular too so there could very easily be two “Isla Jones” at school or work). Pros are: more people will like the sound of the name than not, most will be able to say and spell it, will “fit in” with their peers, can buy tat in shops with their name on etc etc. Hope that helps a little ❤️
ETA: Btw I doubted my sons popular name for a while too (and it’s a completely timeless one, they are easier imo to find for boys). I think doubting is commonplace, no matter how many boxes a name ticks! For me it only completely went when he started referring to himself by his name- he won’t even use a nn, as far as he is concerned his name is his name iykwim?