For better instrument sounds you might try the Timbres of Heaven sound font. I used it for a while to obtain a more realistic plucky banjo sound than I was getting from my Mac's built-in midi instruments. I learned where to install it so my tablature writing/playing software, TablEdit, could find it. I ended up removing it and reverting to the Mac's built-in sound font because plucky wasn't the right sound for some of the pieces I was working on.
But many of the instruments do sound better than the stock built-in midi instruments.
Here's the main page on ToH:
https://www.midkar.com/SoundFonts/index.html
There's a lot to read. A lot of it technical.
There's a fairly active midi group on Groups.io called MIDKAR (midi and Karaoke). Here's its home page:
https://groups.io/g/MIDKAR
It was through this group that I eventually learned exactly where to find the Timbres of Heaven soundfont and how to use it on a Mac. Of course, it works in Windows, too.
Be aware: depending on how you install it, its instruments can replace the midi instruments you're used to seeing in a menu.
Also: Remember it replaces only the sounds of the instrument. Notes and rhythms come from iReal.
Beyond that, I'm no able to offer any help. For those with a technical bent who know how to undo things, this can be worth trying.