His uniqueness has not disappeared. No other civ gets those bonuses upon conquering a city.
Bonfireg did not call it “broken” as in OP - he said it was broken because the mechanic was not working as intended. Read the ability description and look at the code and it’s clear the point was not to let you get these boosts by building the districts AFTER you conquer the city. That doesn’t even make thematic sense for the ability.
So yes, it was broken before and your play style was relying on an exploit; it’s no different in principle than devising a strategy based on the infinite pantheon glitch.
When you read civ ability description, you would notice it is supposed to grant eurekas and inspirations from distrits in conquered cities, not specifing the moment of conquests (so completed districts gave boost immediately, pillaged districts when repaired, not existing districts upon buying/construction). This is how hellenistic fusion works - combining local cultures to benefit nation progress. And intuition says loal culture does not dissapear magically in one turn.
Ergo I would not expet "that was the intention of developers", cause I can only guess by uniques desriptions (i cannot read the code, I am from previous era)
Especially when Alex's leader ability is explained in different way - it says directly "when you conquer a city, all units are healed".
If any Macedonian abilities were not working as descripted, it was "to the world's end", not "hellenistic fusion". Suddenly we have TTWE not fixed, what could be expeted, while HF "fixed" while not necessairy expected.
EDIT
First look on Macedon
gives much clearer view on what was the intention, so I agree it was not exatly working as wanted.
If it was bug and exploit, then huge congrats Firaxis. Macedon was in first civpack DLC released in march 2017 and it took 4 YEARS to notice it and fix this?
Still this single fix is probably the biggest nerf ever experiened by a single civ. Pretty reasonable if the civ was already overpowered, but Maedon was not so OP with NFP, and now diretly is moved to the very bottom tier.
And yes, Macedon still gets rewarded from conquering cities, but this reward is minimal (how many boosts you would be given from conquering in lassical era? 4 boosts total per civ on deity on average, really devastating amount) , while still lacking civ speific tools to make conquering cities easier. Espeially after classial era.