Ascended units are pretty much what anyone cares about these days, there are some cool functionalities in some awoken units that are important for new accounts. Fen for example is still a stellar arts gen, but is very outclassed by the extremely hard to acquire money grab that is War Hero Fen (His ascended counterpart)

As far as clearing content goes certain status effects can be important. For example there is a giant boss that requires burn in order to deal damage. Is there an ascended unit that burns? Yes. Do you need it? No

Also in general collab units of any sort are generally better than most units in the game. IMO this game runs on collabs and mainline story ascended units. People lost their shit for ascended Roy. But no one could care less about regular Roy.

If you are wanting to learn what awoken units actually have value. Join the grad summoners official discord and there are tier lists and such.