Original sin affected us in many ways- You’re right about the loss of grace- That is the hole/lack that Catholics name “the stain of original sin” which is taken away at baptism, when we are infused with sanctifying grace and gain a communion with the Blessed Trinity, now living in our souls. It’s what Catholics believe happened to Mary at conception who was made full of grace, I suppose you could call it a one of a kind, special “baptism” instituted only for her in view of Christ’s merits (I think of it as a loan of sanctifying grace from God, to be paid for by Christ’s sacrifice yet to come)
But original sin did more than this- The evidence is in Saint Paul’s complaint about the law of sin in his nature at a point when he was obviously in the state of sanctifying grace, and free of “the stain of original sin”. Adam was not made with a tendency to evil or selfishness in his will- He had only a tendency to good; Neither was he ruled by his passions, they perfectly obeyed his reason and will, so he suffered from no attachments to the flesh, the world etc- These are effects of original sin that do not constitute the stain of original sin discussed above, but are also realities in our nature. These effects in our very nature remain long after we are baptized and have been following Christ. They are the reason why we still sin when we don’t really want to sometimes, why we have to struggle against ourselves, the flesh, the world, even the Devil (who through these weaknesses in us has gained a manipulative power over us) even when we are living in Grace.
None of these belonged to man’s nature as he was created by God originally, so our very nature is not as it was, it’s fallen, though still good- crippled, but not totally corrupted, which is why it’s redeemable. Catholics believe that Mary was filled with Grace to the point that affected her entire nature, so that the flesh that she passed on to Christ was totally integral, like Adam & Eve before the fall. Ours takes stages of grace working in us to get to what happened in Mary.