Nope, that is not true.
First of all, you still get a doubled bonus from Fanatic Ethic over normal ones. Since many of these bonus are -% reductions to certain aspects, they increase immensely in value.
I.e. going from Neutral to Authoritarian reduces all Resettlement Costs by 25% (or more, if you already have other boni, i.e. from Nomadic, since those stack additively). Moving from Authoritarian to Fan Authoritarian, at first glance, only adds another 25% reduction, but in gameplay this means a 33% difference (from 75 to 50 of the original value).
Similarily, stacking Fanatic Materialist with Machinist and Synthethic Ascension makes for ludicrously low energy maintenance per Synth Pop.
Additionally, there's the special planetary edicts unique to Fanatic Ethics. Albeit some of them are still of questionable use, especially with the overflowing Influence early on (due to Faction Management), most still provide substantial edges. I.e. Fan Spiritualists +15% growth, or Fan Xenophobes +20% Unity.
Furthermore, having only 2 primary ethics makes it easier to manage Factions, because innately you will only have to deal with 2 large Factions (and you can effectively affirm which faction will spawn first). Of course that will splinter off in the later stages of the game, but it's still an edge that Fanatic Ethic starts have over 3-ethic starts.
Lastly, the biggest (my subjective oppinion) advantage of going 3-ethic, namely the access to unique powerful buildings and technologies, was completely removed. Ethics now only increase the weight of the techs (i.e. the Map the Stars Materialist one), but are not mandatory requirements anymore.
Thus, I think saying that Fanatic Ethics have absolutely no place in Stellaris is simply not true.
Of course, whether they are, in specific situations stronger or not, is an entirely different question, and I will not try to claim that there aren't some Fan Ethics that don't seem to justify their costs.
