Doesn't old kernel images get removed after some time?
They are on a "default" use case, but if you're using systemd-boot you are responsible for configuring a nice way to keep only the last kernel images on the ESP (it's not hard to do) and automagically update it.
If you're using the Debian's default Grub2, you should be using less than 1MiB.
Samuel Henrique O. P. [samueloph] Técnico em Informática - UTFPR [2012]. Estudante de Engenharia de Computação - UTFPR.