3.15lbs. ROFL.
Yes, it's versatile, but I always find myself pegging 70mm -- especially for things like portraits or other shots where compression can help isolate. It's not quite enough range to be a single lens solution. Shooting a 28-105mm, imho, was a much better compromise.
You appear to be looking primarily at the issues with the 24-70 lens, from your PoV.
I love a boring lens. I just want it to do the job.
As you said, it's versatile.
If I need the optics of a prime, I would use a prime, rather than a zoom.
If I need speed, I would consider the f/1.8 primes for more speed, over the f/2.8 zoom.
But you use the primes at the cost of losing the FL flexibility of the zoom. Do I need the FL flexibility of a zoom, or can I live with the fixed FL of the prime? If I NEED the FL flexibility, then I have to use the zooms, and live with the lesser optics and 1 stop slower speed.
If I have a need to go past 70, in a single lens, I would use a lens that can go past 70. Like the 28-105 you mention, or the Tamron 35-150/2.8-4.
Having a 24-70 + 35-150 + 70-200 kit with the considerable overlap may seem unreasonable, to some. However, I have a similar overlapping kit and it works, for me. Each lens has a purpose that the other overlapping lens cannot meet, or cannot meet well.
There is no ONE lens that will do everything you want it to do. A Jack-of-all-trades, is a master of none.
A lens is simply one of many tools in the photographer's tool box.
It is the photographers job to select the best tool for the job.
The practical issue for that tool box of lenses is cost.
You can't afford every lens for your tool box, so you will have to compromise when building your tool box.
The 80/20 rule comes into play. If I will use lens A 80% of the time and lens B 20% of the time, I would put my limited $ to lens A. For lens B, I would consider renting, for the few times that I would use it, or just do without.
If I NEED that 20% lens, then I have to budget for it.