I'd take Barnes over the 12 pick every day of the week and twice on Sunday. He fits this team perfectly. He can start at SF, can play PF, is a good defender, good team player, can shoot, stretch the floor, etc. He just fits perfectly. Right age, right talents, comes from a winning organization. Barnes is better than the 12 pick any day of the week. I'd trade that straight up.
The Burke for Lee part? Neither team cares about either player. Lee is at least an NBA player. Im not sure you can say that for Burke.
The reality is that trade would probably have to be:
Burke, Booker and #12 for Lee and Barnes.
Trading Booker is tough, but reality is, Booker probably isn't in Utah's long term plans, while Barnes could be. I'd still do that trade.
GSW cares about Lee! As in ... they are desperate to get rid off his salary, otherwise they wouldn't be looking to deal him. This is called liability. When you take a liability off a team, you receive value elsewhere... i.e. draft picks, valuable players and assets, etc. Example, we take on Novak's 2x3.5 mln contract(liability) and we receive 2nd round pick by doing it. JaVale McGee (11m) to Philadelphia for first round pick. In general, taking up to ~5mln results in a second round pick, taking 10-15M(and here Lee is on the higher end) you get firsts or multiple picks. That's been the market so far and I don't see why we should get away from that. Taking Lee's contract is about the price we should be paying for the likes of a player like Barnes. You simply never should pay more than is enough to get a deal done. Why would you include our first round pick(lottery) if a deal can and should be done without it?
That's like going to the store demanding to pay 40 bucks for a 20 bucks item.