IMO the trim is the best thing about the house in front but I have to say I dislike houses that are completely different on the back than on the front. Is there a reason for the patio part out front? I think some color blocking might be the answer . These are just a couple of ideas of what it is probably not as extreme for your place but it sure would make the back of the house more interesting but it needs to be designed to also go on the front.I usually like the green for your siding but I find it just kind of blah on your house. The color blocking takes some skill and so you would need to find someone good at it.

These are a bit more subtle and would also work on your place

I like your house, especially the color. Just needs a climbing vine in magenta to show it off to its best advantage.

Seems to me there are plenty of new adhesives on the market that would allow you to add the white trim to the stucco walls. Also, I would not use wood trim, but some of the lighter weight composites that don't warp and come prefinished.

https://azekexteriors.com/products/trim/trim-boards?gclid=CjwKCAjw4871BRAjEiwAbxXi2zq7wLWsNzH_CsPMUzQAa092IU54fKwoiGVv9JlgLx6u2RVGLYcN4hoC59UQAvD_BwE

I would paint it all out in a soft white and add some modern lighting and new larger house numbers add a bench in front of that window with some plants to dress up that front patio area.

Nice large modern house numbers add some black planters and dressing up your patio area perhaps even adding a pergola!

I really like the above suggestions from @likewhatyoudo. Especially like the striking black garage door. Maybe you just need a 3rd color added to the palate for the garage and/or front door?
@PatriciaColwell, I’d love to see what you mean for the color blocking to her house. Would you use the current trim as the borders? And what about the back? Would you be able to photoshop one of her pics as an example?

A less expensive fix than ripping out all the wide trim boards.

Begin by painting the horizontal trim boards that are across the face of the siding located between the floor levels so they're the same color as the siding. Do paint that small part of the upstairs window vertical trim boards that extends above the horizontal trim boards The rest of the wide trim boards around windows and doors I actually like.

If, however, the wide trim around the windows and doors still bothers you, then ( except perhaps for the fascia) begin by painting all the rest of the wide trims the same color as the siding. Once that is done, add narrower boards in the contrasting trim color atop the wider trim boards around the windows and doors.

Like the idea of a pergola on the back -- something more structured ton which to hang your lights.

The color blocking mentioned by Patricia Colwell Consulting -- sorta like exterior accent walls -- would certainly help break up the monochrome back wall -- perhaps the center part left/by the chimney and the chimney as well.

Your house white with black -- black for the color blocking, trim and metal exterior lights could look really good (though I suspect the striking black garage door might work better on a lower level rather than up front and center on the main house level; however, I'm no pro). Perhaps someone in this discussion could photo shop a pic of the black/white options with a black garage door for you. (I really would like to learn how to do that.)

Paint the wide trims to match the body color. They are now defining your home as a boxy building, but if they fade away you'll get a sense that the house is larger. I suggest you be daring and go for charcoal gray with cedar garage door, front door and cedar cladding on the gabled bumpout on the second floor. Remove the wide trim from the front windows so they match the ones on the back.

Thanks everyone for the great suggestions.