Frankensten,
You have got a bit of a mauling from your less than helpful Logic community.
Basically, when you mix audio in the conventional sense as you are doing, you are making sure the sum of all tracks does not exceed 0dB. Kicks and Snares and the odd sharp attack of a vocal/guitar/keyboard are always going to take you up to that level so when everything is playing in your final mix, the quieter parts are going to remain just that...quiet.
In order to make your music sound overall 'louder', like it does on the radio/cd's, you use clever processing that a) momentarily reduces the volume of the louder sounds and b) increases the volume of the quieter parts.
The 2 processing tools at your disposal for this magic are a) Limiters and b) Compressors
I am not going to describe the physics behind what these 2 do to the sound, as the Logic Pro Help chapter does a fine job, but for a short solution to your needs try the following.
Insert a multiband compressor and an adaptive limiter in your master output (in that order). For starters, try one of the menu options for an initial setting and adjust to taste on each one - The 'Add Density' option on the adaptive limiter is a pretty good starter for instantaneous volume.
There you go! A significantly 'perceivably' louder mix with the meters still remaining less or equal to 0dB➖
Top tip. Most music systems don't have speakers capable of producing sound below 40Hz. Insert an EQ in your master bus before the compressors and adaptive limiters and roll off everything below 40Hz. You will discover a whole load of energy that is imperceptible to the mix disappears from the mix allowing an even louder mix output.➕
➖=Excessive use of limiters can cause something similar to having one's head put in a vice 😉.....repeatedly on every beat.
➕=Unless of course, you are a sub-bass junkie
