it's that there's not enough pressure. There are flushing systems that can produce a lot more pressure even when only using a small amount of water, but I don't think I've ever seen one in a home in the US.
Our toilets are much the same here in Canada - residential use toilets are gravity-fed with typically 6L per flush from a "close-coupled" tank which is mounted directly on top of the bowl. The tank is filled from municipal or well supply, which is typically at 50PSI or so, but the fill valve is the only part of the system under pressure.
They operate by momentum, not by pressure. m1*v1 = m2*v2. The pressure would be limited by the head, which is typically only 2 feet or so. The secret to their effectiveness is allowing 6 kilograms of water to accelerate as quickly as possible in the height allowed by the design and have it collide with the ...dark matter... to drive it away.
Most residential plumbing systems use 1/2" ID supply pipe which would simply not allow a pressurized flush like a commercial toilet to be effective. There are exceptions which use bladder systems to attempt to leverage the standing water pressure of the municipal water supply to drive the flush water down to the bowl as quickly as possible. These systems tend to be expensive, unreliable, and loud, although one day these issues may be resolved.
Improvements to the existing system will require very carefully designed bowls and trapways and exceptionally well-installed plumbing with regard to soil pipe slope and venting. My own home is outfitted with 3L per flush toilets which do an admirable job - I have yet to clog them, even after a visit to a buffet restaurant - despite being purely momentum-based close-coupled toilets without the additional complexity and failure-prone seals in dual-flush mechanisms.
Adding technology is not the answer to this problem. Keeping it as simple as possible but doing the basics really well is key.