Perhaps you missed detail in that dev diary. Your empire overall does not have some abstract level of attraction for each that is universal to all pops and they'll all share it - the attraction across your empire shown in the screenshots is aggregate of the attraction to them by different pops
You're wrong. The screen shot they showed of the attractiveness of the Authoritarian faction had four different empire wide affects that either add or reduce the attractiveness of Authoritarianism. These aren't aggregate from the individual populations response to your empire taking Domination Traditions. Some affects, like being in an autocratic government or your empire having Authoritarian Ethos, will create a set amount of Ethos attraction that guaranty's a certain percentage of your population will shift towards that ethic.
Nothing in the dev diary says that they've removed the concept of ethics divergence - in particular, nothing says they've removed conformist or its counterpart.
They either removed it, or revamped it so heavily that it is no longer applicable to your complaints and no longer suitably described by the term Divergence. Either way you're splitting hairs here. Ethics divergence used to operate either by shifting your population either towards your empire ethos, or away in a random direction, thus the use of the term divergence. Your strategy was 'mind control lazers' 'unity temples' and 're-education plants.' In the long term, you converted deviant populations to your own ethos and you stopped having problems with them. You still seem to think this is how it will operate despite presumably having read the explanation that it no longer will operate that way.
As of Utopia what happens is that your populations will shift ethos to reach a mean close to the attractiveness stats that you can see on the page I linked. This mean is reached by a combination of local affects AND empire wide affects and populations affected by these local affects will also have a higher percentage chance of being the ones that shift into that ethos to bring you up to the mean. Mind control lazers may still be a thing, but if they do anything, it's going to be a bonus to the attractiveness of your empire's ethos, it won't be flipping the switch on some populations so that their ethos shift towards you instead of randomly away from you.
You presume I aim to deal with it by purging. I'm looking through individuals to see what their ethos are, figure out why they're different, determine if this planet needs attention in that regard such as symbol of unity or orbital mind control laser, or if I just need to give them a bit more time because it's not been very long. Things are greatly obscured with all the synths being the same, regardless of who created them, except in some back-end factors you don't see.
If you're looking through individuals anyway, no information is obscured and the portrait picture gives no additional information, likewise if you're looking at individuals anyway, the race of their creators provides no information regarding the use of an orbital mind control laser or a symbol of unity. Really, that kind of information is only useful if you're making off the cuff judgements based on racial origin. And if you are making off the cuff judgements based on racial origin, you're in for an even bigger disappointment. Take another look at that most recent screen shot of the Commonwealth of Man. Those fanatically militaristic humans only have an ethos attraction to militarism that's just over 40%. If you conquer the commonwealth, see a human, and assuming he's militaristic you will be wrong almost 60% of the time.
And all of this is predicated on the assumption that the AI will even regularly take Synthetic Ascension as a path. Because the benefits of Synthetic Ascension are a bit more oblique in regards to the standard strategy for play. And given that maximizing the benefits of Synthetic Ascension requires long term planning. And given the AI is bad at both dramatic shifts in strategy mid game AND long term planning, Synthetic Ascension, much like reforming the HRE, is probably a toy for human players. Not the game's AI.
And as for multiplayer, if you've found some multiplayer partners who actually sit there while you sort through each individual population without abandoning you completely, you are so blessed in your life already that you'll survive adapting to these changes.
Found an even better point. Return to post 1 in this topic. The icons for "Conformist" and "Deviants" are still available traits. Ethics divergence on an individual level is still a thing, just less random where they diverge to, and no longer happening with distance.
Them continuing to use an icon is not a better point. Never have they ever thrown out a perfectly serviceable piece of graphic design while creating an expansion and that they chose to continue using the icon for "conformist" after either reassigning it to a different trait or reworking the conformist trait so it's compatible with the changes in Utopia does not prove that "ethics divergence on an individual level is still a thing."
Ethos shifting on an individual level is absolutely still going to be a thing. But it won't be the ethics divergence you think it is.