Names that became popular because of a celebrity/fictional character.
Names that have certain sounds when there are lots of similar names.
e.g.
Evie, Ava, Ivy, Eva, Ev- names
El- names like Ellie, Ella, Elsie...
L names like Lily, Isla, Lyla, Lyra, Lola, Luna
May names - May, Mabel Maeve
Old Testament names other than the ones that never fall out of use.
Names ending in -ie or -o for boys (.Leo, Hugo, Archie, Alfie, ...)
Names that parents choose because they are 'a bit different' but many other parents have the same idea. (Chloe is an example, going back about 25 years, Arlo and Luca more recent ones)
Names that are just too popular (Sophia/Sofia, Theo/Theodore)
Names that get associated with less-desirable social classes.
Nature names (Rowan, Willow, River)
Names that don't really sound very nice (Margo, Freya).
Families/friendship groups can become saturated with similar-sounding names.
Once you start feeling you're in a garden or on Emmerdale, you might start
looking for fresher-sounding names.
Solid classic names never date and are used consistently across generations
I agree. If they aren't overused but remain in use, they don't really date, or they may not date badly.