There's some interesting consequences arising from the mental load concept, though, which directly opposes reaching consensus of what counts as "enough".
If we accept that mental load adds to the overall perception of total workload, then even a partner who does 50% of all chores, or 100% of "their chores" isn't making any inroads into reducing the "mental load" of the other partner - the load still exists because that partner still needed to plan/organise/worry about it.
In corporations, the exact same relationship exists between blue collar and white collar workers. The people holding spanners genuinely believe that they create all the value because they do the physical work, whereas the people in the boardroom think they create all the value because they make high-stakes decisions about whether to hire more workers or invest in robots. Management carry all the "mental load" for corporate success, but are much better compensated because of it. Workers get an hourly wage, insist on overtime, and get to walk out of the door when the shift finishes and generally care less about the wider success of the company.
In partnerships where one partner has a white-collar mindset (mental load), but is doing the blue-collar work (dishes), of course there is going to be dissonance. If the other partner is a blue-collar worker, then the couple's problems stem from the fact that they are doing two lots of blue collar work, with one of them expecting white collar pay and perks. But the money doesn't stretch that far.
In partnerships where that partner does white-collar work, there is a better chance that the blue-collar work in the home can be outsourced to cleaners, gardeners etc. but the tension is merely reduced rather than eliminated.
It is only in partnerships where the housework is accepted as blue-collar, because the stay at home partner is genuinely blue-collar in their mindset - they know what constitutes "enough", take pride in the work they do in and of itself, and are willing and able to down tools once they've ended their shift - that there is any prospect of harmony. But that violates the first rule of feminism, which is that it should be possible to have it all. The sex of the partners is less relevant than their mindset.