I actually don't mind it so far, it's more realistic. My only complaint would be to get actual real feedback on why the trade didn't go through from the other team, it's too vague right now. Maybe a better way to do this would be an interactive communication with the opposing team. Allow me to ask them about a specific players in the trade offer to understand if they even want them or if they are the reason why the trade is getting held up, etc. etc. etc.
If you want the "instant trade" kind of feel, you can always send out an offer, create a save point, sim ahead to get the feedback, reload the save and try again. Kinda lame and not in the spirit of the game, but if you want 50 trades to happen within a day, to each his own.
I also don't necessarily like the black-and-white untradable players idea. Everyone is tradeable for the right price. Maybe another example of when an interactive conversation with the opposing GM might prove useful. Let me talk them into it haha. I've been waiting for Trey Yesavage or Connelly Early to be available for 3 seasons but they're both on lockdown and at this point they haven't grown at all and my team is gonna be worse if I trade for them. Counter point though, who is realistically trading their $800k per year restricted star pitchers in real life? IDK, now I'm torn on this entire thing...