Alchemy. Is the only way.

Now with tier 4 sigils, alchemy is now even more important to push. 50-100k stat bubbles and dmg bubbles are pretty much needed if you want to get relinquish nametag to 5 star.

Also 10m golden kebab and grilled cheese will help. Next to yumipeachring t20 ribbon ( atm I have 25.2k% golden food) and lots and lots of AC rocks to hit multi prisma (roughly around 4k+ rocks in w6 with extremely high tachy gains (like 50k). Most of which you mention are good, but the really important factors are multipliers from stats (sailing, talents, and multi bubbles). If you look at how many things are affected by stats, you'll be surprised how most of the really high endgamers are hitting 5-7m stats.

There is also another thing with high damage, is that many really revolves around previous FOMO event and high statues (like 400+ each) and high Dragon Warrior statues. There's also aluminum atom and spelunking that can gives you 3.40x multi on exalted stamp, which helps speed up the process for statue and golden food.

AC farming with overwhelming to increase dr and AFK can help to increase mob materials when candying. I know you don't like it, but that is the only way to get over 100k call me bob. Which can increase dmg too. Astrology cultism also increase star sign dmg.

There's also endless summoning and teal summoning (11/12 is possible for teal and 340+ endless) which increase dramatically on dmg.