Is it the batteries, or is it the cameras?
My 5 D IV is a real "battery-eater", unlike my EOS R. I've never succeeded to get more than 450 shots (no bursts!) from the 5 D IV, but more than 800 from the R (no bursts).
My issue is rather durability of the batteries, 2-3 years max. despite careful use and energy efficient settings.
Leica M 240 battery: 8,5 years old, and still good...but horribly expensive when replacement is needed.
3 things really:
Battery performance - this would probably require Canon to develop a physically larger battery, ruling out backwards compatibility, but it's feasible they could squeeze more performance and longevity per charge while retaining the same battery format. There are valid arguments in favour of backwards compatibility, but personally I'd rather that Canon just moved on, and produced the next generation of cameras, using larger and better batteries.
Camera electronics - unfortunately Canon lag behind Sony by a considerable margin here, which is unsurprising, given Sony's long history with electronics. I'm no expert on electronics, but from what I've read and heard, Sony uses much more advanced circuitry than Canon, which places less demand on batteries.
Usage - some photographers will leave a camera turned on for long periods, or spend long periods with finger half-pressed on the shutter, in anticipation of a shot. Some photographers will set the camera to the fastest refresh rate, and have the EVF and sleep timers set to 3 minutes or longer. Others will only switch the camera on just prior to taking a shot, and then turn it off until the next shot. Some will be shooting mainly single shots, some shooting long bursts, some shooting video. Shooting style has a great impact on shots-per-charge.
My R5 battery life roughly corresponds with the CIPA figure of 320 shots per charge.
My 5DMkiv battery life averages about 600 shots per charge (LP-E6NH in both cases).
Regarding durability, I think 2 years is an acceptable lifespan, but a lot will depend on how many recharge cycles the batteries get.