The Iran deal is actually rather simple in concept. Iran temporarily suspends certain nuclear activities (not all of them - for example, researching enrichment is fine). In return, Iran gets an economic boost and a permit to do whatever it wants, like supporting terrorists or mass murdering Syrians or trying to destroy Israel.
The latter part may surprise you, but it's obvious when one thinks about it. What is the West allowed to do when Iran commits those things? It's not economic sanctions, since removing sanctions and then placing them on again for different reasons would leave Iran no reason to comply with the nuclear deal. And of course, war is undesireable (the entire point of the deal was to avoid war). So Iran can do whatever, and if the West does anything serious, well, nukes.
The rest of the ME isn't going to meekly submit to Iran. Worse, Iran can't finance its holdings (Iran requires weak governments in order to hold Iraq and Lebanon, but that means no investments). That means things get done in the ME way, which already leads to mass amounts of refugees.
Iran's involvement in Syria directly led to Brexit (Leave would have lost without an immigration crisis on) and played a key role in Trump getting elected (Is it a surprise the most anti-immigration R candidate won the primary given that background? Didn't Trump end up hiring Cambridge Analytica, which would have never happened absent Brexit?). If it weren't for the deal, maybe the US would have done something about Syria and we'd have avoided all that. If Iranian destablization of ME restarts under Biden, the result may well be Trump mk2.
I do not believe this is an acceptable price for temporary restrictions.