If your CDs are playable on a CD player, (rather than a computer),
then format-wise your audio is the same quality as store-bought CDs.
If your CDs are not as loud as store-bought CDs that could be due to the dynamic-range-compression applied to professional recordings.
If you want to participate in the loudness war, you need to use a multi-band compression plugin, (before burning to CD).
ToneBoosters “Broadcast” (v3) is good free one … Free (v3) ToneBooster's plugins - #3 by Trebor
it has presets …