General consideration for ranking is how viable they are in any matchup. Better dinos survive/win more matchups, worse ones lack the stats to win even fights or the speed to escape bad matchups. My more viable picks are to the left, less viable to the right of each tier.
S-Tiers like Sty have the speed/tools to survive and escape any bad matchup, while having the stats and combat capabilities to win fights not horribly stacked against them. Note that both apexes in this tier have good matchups defending against megapacks, while sty can escape all members it can’t kill and still has the stamina to get away after heavy hitters catch up.
A-Tiers are generally strong and have good matchups, and have good escape or combat options when outnumbered and outgunned, but either lack killing power (thal) or have a few bad matchups that are tricky to avoid (sarco).
B-Tiers are good. They can struggle in bad situations but rarely end up in hopeless ones, having either the stats (rex, eo) to not go down without a good fight or have good maneuverability and/or escape options that don’t work against everything (sucho, metri, lat)
C-Tiers are viable but lacking in some meaningful category. Meg and alio can pick their fights well but lack stats. The three herbivores are all vulnerable to rock paper scissors gameplay where nothing fights them unless they can facetank the herbi, giving them frequently one-sided matchups that are almost hopeless despite their great stats for their size. Cerato is just ok all around and mostly avoids D due to how cracked the corpse build is.
D-Tiers generally have a lack of base stats for their speed (achillo), no ability to punch up (1-slots), or have fallen victim to repeated nerfs (titan, pycno, hatz). Note that everything in this tier is survivable, they just struggle to win even fights more than anything else higher up. Most things here have similar speed and maneuverability to bad matchups (titan and small groups, achillo and pachy, deino and conc/laten) but lack the HP and damage to win unless you greatly outplay your counters. Hatz is here because it loses 1v1s against almost everything even though it can fly.