It doesn’t help yet, but next level (at 9th) the sorcerer can pick up Animate Objects. That spell is a dramatic change in overall combat power for any class that can cast it, when used on ten tiny objects (a bag of daggers works great). A sorcerer can cast it quite a few times per day by converting lower-level slots to additional 5th-level slots via sorcery points.
Polymorph (turn allies into giant apes and t-rexes) and Counterspell are other significant spells the sorcerer has access to that the clerics don’t. Plus things like twinned Haste that you already mentioned.
There’s also the Transmuted Spell metamagic from Tasha’s that would let the sorcerer convert fireballs to acid-balls or other elements that are uncommonly resisted.
Sorcerers do feel like they’re in a tough spot, and picking blaster spells (except fireball) can feel underwhelming. 5e is generally good at avoiding “trap” choices when building a character, but sorcerer is probably closest because it’s so dependent on spell choice, and picking the right spells takes experience.
There are some great spells that last all combat (web, haste, polymorph, greater invis, animate objects), and those plus fireballs and cantrips can add up to a pretty good package. Outside of combat... the sorcerer spell list is decent, but you have so few spells known that it’s hard to have interesting options available for a variety of situations. The Magical Guidance feature from Tasha’s can help sorcerers somewhat with skills.
Lightning seems viable but lacks a ranged cantrip.