Why does substituting eval with declare (for creating dynamic variables) result in an empty variable?

With bash >5, I'm trying to assign a different value to variables depending on the architecture specified in a variable. I use a function to do so. This works perfectly: # arguments: variable name to assign, value for mac arch, value for pi arch create_variable_for_arch() { if [ "$_run_for_arch" = "mac" ]; then eval $1=\$2 else eval $1=\$3 fi } However, this breaks my script for some reason: create_variable_for_arch() { if [ "$_run_for_arch" = "mac" ]; then declare "$1"="$2" else declare "$1"="$3" fi } Here is a snippet to demonstrate how I use create_variable_from_arch()

declare _moonlight_opt_audio
declare _arch_specific_stream_command

#
while getopts "b:fahdr:s" options; do
  case $options in
    a)
      create_variable_for_arch "_moonlight_opt_audio" \
        "--audio-on-host" "-localaudio"
      ;;
  esac
done

create_variable_for_arch "_moonlight_opt_fps" "--fps 60" "-fps 60"

start_streaming() {
  _arch_specific_options="$_moonlight_opt_resolution $_moonlight_opt_fps $_moonlight_opt_audio $_moonlight_opt_display_type $_moonlight_opt_bitrate"
  create_variable_for_arch "_arch_specific_stream_command" "$_arch_specific_options stream $_target_computer_ip $_moonlight_opt_app_name" "stream $_arch_specific_options -app $_moonlight_opt_app_name $_target_computer_ip"

  moonlight $_arch_specific_stream_command
}

The trace looks like this with eval()

+ start_streaming
+ _arch_specific_options='--resolution 1920x1080 --fps 60   --bitrate 5000'
+ create_variable_for_arch _arch_specific_stream_command '--resolution 1920x1080 --fps 60   --bitrate 5000 stream 192.168.1.30 StreamMouse' 'stream --resolution 1920x1080 --fps 60   --bitrate 5000 -app StreamMouse 192.168.1.30'
+ '[' mac = mac ']'
+ eval '_arch_specific_stream_command=$2'
++ _arch_specific_stream_command='--resolution 1920x1080 --fps 60   --bitrate 5000 stream 192.168.1.30 StreamMouse'
+ moonlight --resolution 1920x1080 --fps 60 --bitrate 5000 stream 192.168.1.30 StreamMouse
moonlight --resolution 1920x1080 --fps 60 --bitrate 5000 stream 192.168.1.30 StreamMouse

But with declare it looks like this:

+ start_streaming
    + _arch_specific_options=
    + create_variable_for_arch _arch_specific_stream_command ' stream 192.168.1.30 ' 'stream  -app  192.168.1.30'
    + '[' mac = mac ']'
    + declare '_arch_specific_stream_command= stream 192.168.1.30 '
    + echo moonlight
    moonlight

$_arch_specific_options ends up with no value. What is going on? I've tried a few different ways of quoting or not quoting variables, but I don't really understand what's doing what in terms of quotations.