Couple of things here. Si, this isn't the rest of the world. This is MLS. Welcome to a league with ridiculous roster rules and player acquisition rules.
Dos Santos was happening whether TAM was became a thing or not. LAG had already come to an agreement to renegotiate Omar Gonzalez's deal to make space for Gio. Gonzalez was on board with the idea.
Outside of that, every large name DP you named was signed by a team that already had an Open DP slot. Something the Sounders do not. Again, MLS roster rules are a thing. it sucks. But we cant just go out and buy Dani Alves because we need a better starting LB.
Signing a DP, and hell a player in MLS in general, is quite a task for teams. There is the play "Discovery" process in the league which Bruce Arena has pretty much said is a big flustercluck. Essentially if you are thinking you may want to sign X player, you have to file a discovery claim with the league (yes, Drogba and Pirlo had discovery claims filed). Once that is done you can begin to negotiate with the player. The Sounders filed a Discovery claim on Valdez in 2012. Lord knows how long ago for Ivanschitz. Hell, Montreal didn't even have discovery rights for Drogba...they had to trade with Chicago to get them....
There are a lot of moving parts that need fall right to sign a player of that caliber.
As for Fredy Montero. Further "MLSing" would be required to get him. He would fall into the allocation order as a player returning to the league (we don't own his league rights). As such we would need to move to the top of the allocation order (like we did Dempsey) to get him.
You keep mentioning a lack of young talent on the squad, but we have talent and they are getting their minutes. Kovar and Roldan got the start tonight for instance.
I don't think it matters whether we knew about the players or not. I know of Valdez because I researched him when we were rumored to sign him a few seasons ago. I don't know of Ivanschitz...but I didn't know Christian Tiffert, Blaise NKufo, Mauro Rosales, Alvaro Fernandez or Fredy Montero until they got here either. I don't think its fair to hold the fact that the players are "unknown" by the fans thus meaning they can't be excited...
The signings will help fill areas of immediate need for the team. Ivanshitz will add depth to the outside midfield, and potentially could play in the middle a bit infront of Ozzie for us. He's not as fast as a player as I was hoping for, but his ability to deliver the ball to forwards is something we need. He also appears to know how to make a late run into the box from the midfield....We only have one CM on the roster who is capable of that type of run, and he is starting at CB.
Both players add goal scoring threats from players not named Clint Dempsey and Oba Martins which is exactly what we need. We need goals from more than 2 guys....cause when they are off, or hurt, we don't score.