(setq package-enable-at-startup nil) should be in early-init.el

[wickedjargon]

this line:

(setq package-enable-at-startup nil)

should be added in your early-init.el file, not your init.el file. Per the docstring for package-enable-at-startup:

Whether to make installed packages available when Emacs starts.
If non-nil, packages are made available before reading the init
file (but after reading the early init file).  This means that if
you wish to set this variable, you must do so in the early init
file.  Regardless of the value of this variable, packages are not
made available if ‘user-init-file’ is nil (e.g. Emacs was started
with "-q").

Even if the value is nil, you can type M-x package-initialize to
make installed packages available at any time, or you can
call (package-initialize) in your init-file.