They aren’t taken, as such, but you are choosing very popular, very high up the charts, very 2022 names, in the most part. If you’re happy for your Dc to have a popular name, that’s cool, just use one you love. Because with names that high up the lists, they’ll most likely know several others by school age anyway.
If you wanted to choose something that’s currently less popular, say outside the top 500 or 1,000, you’d have more freedom to chose something not already ‘taken’.
Eg Isla (3rd most popular in England and Wales in 2021 with more than 2,500 little Islas born) could become Alisa (only 69 born) or Althea, well outside the top 1,000.
Olivia is lovely, and very popular, first place in 2021 with more than 3,500 born. Others with similar sounds are Ophelia, outside the top 100, Evelina, outside the top 500, Olympia, outside the top 1,000.
Same for boys, Archie, Albie, Albert, Arthur, type of names are all very high up.
Ashley, Aubrey, Arnold, not so high (top 500-700)
Edmund/Eddy, Matthias/Matty, Indiana/Indie, also far less popular.