Is a Ritual Summon still considered a Tribute Summon?
A Ritual Summon is a type of Special Summon, and a Tribute Summon is a type of Normal Summon. These types of summoning are distinct, so ritual summoning Chaos Max will not count as a tribute summon.

Yes, it's true that ritual summoning requires you to tribute monsters from your hand or field (or other places, depending on the card), but tributing these monsters is merely a cost for the special summon. Just because tributing is involved doesn't make it the same as normal summoning a level 5 or higher monster by tributing a monster(s) you control.

However, as an aside, it should be noted that in both the case of a ritual summon and a tribute summon, any effect of the tributed monster that triggers when it is tributed will still trigger (for example, Evoltile Najasho's effect will trigger regardless of whether if it was tributed for a tribute summon, a ritual summon or even a card effect like Big Evolution Pill).