I have not personally used kickstart.nvim, but I would assume it’s using nvim-cmp for auto completion menus.
In my configuration, I have Enter as the key to confirm my completion selection, but I don’t have your issue because by default none of the completion options are selected. This is one option you could use to solve that issue.
You can look at the recommended configuration here to see an example. In the cmp.setup() function, when mappings are being configured, there’s an inline comment that explains using cmp.mapping.confirm({select = false}) will only accept the currently selected item if it was explicitly selected by you (using arrow keys, in your example).
Another option is to change the completion confirmation key bind. I know a lot of people use ctrl-y for confirmation, so that might work well for you too.