I don’t know that being ranked #34 is so popular that it will be a problem. [name_m]Even[/name_m] 2018’s top name ([name_f]Emma[/name_f]) was given to only 1% of baby girls in the US- very different from 30-35 years ago when 2.5 or 3% of babies were named [name_f]Jessica[/name_f], for example. I think it is unlikely that your child will be one of three or four Lillians in her kindergarten class.
I know a few Lillians: my great aunt, a 22 year old (goes by [name_f]Lilly[/name_f]), and a friend’s kid who is 3. I knew two Lilys who are now around 30, and one [name_f]Lilith[/name_f] who is high school age - last time I saw her she was about 5 and went by [name_f]Lil[/name_f], I am not sure if she still does.
Personally, I probably wouldn’t let overall popularity stop me from using a name I loved, but would likely avoid names already used by family or friends I see frequently, regardless of where they rank (I know a surprising amount of little Edens, for example). I wouldn’t think about popularity at all for a middle name.