OP, you have got to be the most selfish, entitled, jealous, unworthy jack*** of a player I have ever had the displeasure of running into on the BSN.
When I PuG, I end up having to clutch a wave or two about every third game. I clutched wave 3 in a Collectors Gold match with a level 1 soldier the other day...with a Locust. I had to kill a few abominations, a few troopers, and two possessed scions. It took less then a minute to kill the aboms and troopers, but the scions took a little bit of time to wear down. I'll be damned if I'm going to waste a missile to kill the last two bosses, when I'm perfectly capable of doing it without. I'll save my Cobras for when I really need them...and if you don't like it--dont die. Plain and simple.
If that's too hard? Go play bronze.
A few notes:
1) CS and ME3 MP are so completely opposite from each other, that simply comparing one to the other is doing them both a disservce. Knock it off.
2) I work 50+ hours a week, go to school, go out on dates regularly, help take care of my parents' house, exercise, get my homework done, make good grades, and still have time to play ME3 MP at a relatively elite level. There are these things called clocks...if you have less than 40 minutes, you don't have time for platinum. If you have less than 30 minutes, you don't have time for gold. If you have less than 20 minutes, you don;'t have time for silver. If you have less than 15 minutes, you don't have time for bronze. Be responsible with your time.
3) "Don't waste everyone's time and keep the game moving forward!" Really? Says the guy who died and is now forcing another player to carry him?

4) "Most of the time they have exhausted their medi-gel." Seriously? This had better be wave 10, platinum...otherwise you need to back the difficulty down. Because you have no business dying that often in any other difficulty.
5) "If you think 'Hey noob, you die so sit and learn'. I'm sorry, that won't make the game better for the less experienced." No, probably not...but it will absolutely make them better at the game if they pay attention to the playstyle of "the clutcher". Which seems to be exactly what they need, if they're dying that much.
6) "I believe a lot of players still carry only 3 medigels with them." Bullsh!t. Everyone's cap was raised.
7) "So you think the busy grown-ups shouldn't play ME3 multiplayer although they like it? Discrimination won't help anyone here." You sound like the black guy at work that claims he's discriminated against because he's black...when really it's the caucasians that are discriminated against--in his favor. Playing the "I'm an adult" card has no place in this discussion.
8) "Oh, so it's my [...] fault when the other 2 players also ask edthe guy to finish the wave faster, but he just runs around with a weak weapon against 2 or 3 bosses." Yes, it is. It's your own fault for dying. Once you die and bleed out, you lose your say in what happens that wave.
9) "It seems I overrated the importance of teamwork in this game." "Teamwork" is
not leaving your teammate to do all the work.
10) I hope you play on PS3. If you do, add me so I can a) see if you're really not the bad player you say you're not, and

if you are, that way I can troll you by finishing the wave with nothing but my Predator (which will be equipped strictly for your spectating pleasure).