Did you expect Iran to abide by it?
I didn't.
You shouldn't have.
No agreement could promise that Iran wouldn't build secret facilities to develop nuclear weapons, and it wasn't designed to nurture the illusion that it could solve the problem of Iran's nuclear development.
The deal was simply the only measure putting any sort of wrench in its nuclear weapons development program, and thereby positioning the US and every other country saying haaaiiilll no to Iranian nuclear weapons to better monitor and manage the threat as it developed.
The terms made it much more challenging for Iran to openly develop nuclear weapons by instituting regular independent inspections of all of Iran's known facilities, among other oversight mechanisms, to enforce Iran's agreement not to develop weapons-grade uranium in them. IAEA already confirmed that Iran had been compliant in this regard up until last year, well after POTUS withdrew the US from the deal.
The US and Israeli IC also were in agreement that the deal effectively would have prevented Iran's 'known' weapons-grade development program for a decade or more, and it certainly slowed down the net progress towards nuclear weapon capabilities by preventing its development in all of Iran's known facilities.
Withdrawing from the deal removed the only existing brake on Iran's development into a nuclear superpower, and this is made all the more clear with Iran's recent decision, after the deal was called off, to openly resume enriching uranium at one of its known facilities.
Whatever the Biden administration ultimately does (deal or no deal - ha!), I think it should retain the sanctions of the Trump administration so it doesn't lose any leverage. I also think that he should take his time and repair diplomatic relations with key EU states that already condemn Iran so that if he decides to renegotiate a deal, he will be in a stronger spot to concede fewer sanctions when doing it, if any at all.