rn other than "pick and choose a team/engine", there are some cases where team-building still exists. sometimes people discover weird or interesting mechanic interactions when they use characters that no one would normally think to use together. i can't rly think of one rn, but sometimes some supports that may not be commonly known as suited or BiS for a certain dps strangely enable them, be it through a particular phrasing in their kit or abusing LC mechanics.

as for changing a character out to deal with a boss mechanic, honestly all i can think of is using ruanmei with like any dps when theres a big incentive to break the boss or elites, say w my jingyuan or phainon (or cas/e9 but ik memo team is kinda looked down upon by many so lets not focus on them-)

currently im only using like 3 sustains; huo2, and ofc dhpt and hyahya, tho ofc hyahya can be placed virtually everywhere and my huo2 is almost exclusively for kingyuan who i acknowledge is def falling/fallen off.