So currently spells that rely on spell attack rolls are inherently worse than saves spells in most cases for following reasons:
Those spell work on hit or miss princle which means that you get nothing if you fail to land a hit which leads to worse action economy because you always need to spend one action on true stike to reliably land a hit.
That also mean that you need to spend two spell slots for one spell which on low levels are to costly
And in most cases succeding in your spell attack dont provide you with much better results than enemy that fail his save against your spell so that big setup not worth it in most cases
So what can be done to make them better?
Obvious solution are
Add potency runes for spell attack while making true strike inapplicable to them
Separate spell attack and saves spells proficiency progression so spell attack can have better proficiency progression overall