You haven't seen the whole show. Maybe the battle for GC, but not the show. Either you don't watch much bike racing, or just outright have no appreciation for all the other days to make a statement like that.
Each flat stage is a different sprint contest, with each one being quite different due to finishes, corners, positioning in the moment, etc. Granted you only need to watch the last 15 minutes of the typical flat stage to get everything worth seeing, but those still have their merit.
Hilly stages are often the most interesting of all the days. Not hard enough for a GC punchup, but varied enough to get some people trying moves at the end.
Disagree as well about the 1-2 "ramp stages" (I assume you mean the especially brutal summit finishes?) deciding everything. Obviously, they can be significant. But looking back we can see last year that stage 9 was only decisive because Quintana raced stupidly on stage 2. If he hadn't lost that time, stage 9 would have been anything but decisive. In 2014 the only decisive factor was that Nibali was ridiculously better than all of his remaining competition. 2013 you could argue Ventoux was decisive, but Froome was pretty dominant that whole Tour. He built on his lead almost every day, and only gained 30s on Quintana on Ventoux. 2012, no ramp issues causing massive separation.
So looking back the last 4 editions I can't think of a single tour that was decided by a very difficult HC summit finish, aside from the possible exception of 2013 Ventoux, but even that would be a stretch in my book.
As for GC stuff:
TJVG: Probably 5th-8th. Strong, but not at the level of the top names and has consistency issues. Probably in a respectable spot until he has a bad day and isn't.
Rolland: Shouldn't even be in this conversation
Aru: Maybe will podium, but my sense is he is a little overhyped. He looks pretty good on his best days, but doesn't seem to deliver that consistently.
Pinot: His TTing seems to be much better. Doubt he can challenge in the mountains with the top guns, but could podium if he can keep it together.
Thomas: Hasn't looked that great and is working for Froome. Top 5 would be an excellent result for him. He's on a similar, but slightly weaker level to someone like Porte, but working for Froome will take it's toll. Podium contender leading his own team.
Porte: At the start I thought he might be the most likely candidate with Alberto to fight for third. He's quite good, but always seems to either get horrible luck or fall apart in 3 week events. He's not that far off the level of Froome and Quintana, but not good enough to beat them either...and of course at 1:45 down has no GC shot unless both crash.
Contador: Looked like he might be able to play with Froome/Quintana, but with the crashes, like Porte he is out of the jersey running unless both of the top favorite suffer mishaps. If his injuries are superficial/minimal he still has a chance to play for podium and/or a stage win or two. If they are much worse than letting on he is going to lose huge time this weekend.
Quintana: Good so far. Last year was really boneheaded by him and cost him victory. He was vastly better than Froome in the mountains. The difference this year is that Froome has some TTs to play with, which could be Quintana's death knell. There are indications his TTing is continuing to improve, but if Froome puts 2-3 minutes into him in the first ITT that could end his chances.
Froome: The favorite, especially with his team. The idea that he is guaranteed to win is one of the most ridiculous things I've read all week however. Quintana is an extremely serious threat to Froome and is without question the better of the two in the mountains. If Froome doesn't deliver an excellent ITT he will likely lose the tour to Quintana.