'Sides the fact that CoD is mostly gunplay (less ya don't count those bloody overpowered Killstreaks, understandably), I agree completely. Instakill traps like mines, proxies, claymores, etc. definitely take away from any shooter if said mines don't do anythin' besides area denial when you're sniping with ya backed turned. You can throw 'em where-ever and get a free kill. Gettin' an amazing kill streak randomly ended 'cause of a bomb 'round the corner is losing said streak through sheer bad luck alone, not skill. Makes for some salty deaths... Salty deaths ain't no fun.
For balancing purposes, none of these "stick 'em and wait" charges should be a one-shot kill. This means you have to risk findin' the time to place 'em in high-traffic areas, since you won't get a kill unless someone who's been shot walks over it. Placed in a more random area, if someone steps on it at full health, you wasted a proxy and possibly gave someone ELSE a kill. This would require a sniper to need some extra awareness 'n skill for proper proxy defense too, as you'd need to keep your ears peeled for a proxy explosion to whip around 'n finish off your injured prey.
... That, or give every game with said insta-kill traps an ability like "Flak Jacket", a CoD perk which reduces explosives damage by 50%. Gotta sacrifice a perk slot for it, but tripwire explosives literally become no more than a meager nuisance. Take cover, recover that health, 'n be on your way. No streaks cock blocked or nothin'.
When playing with randoms, the golden rule is to always assume anyone or everyone is better than you 'till you're an expert, as well as that everyone has better weaponry 'n tools to aid their victory. Hence playing with randoms; everythin' is random. You're up against the odds of a unique metagame where there's no such thing as a fair win or earned loss, there's just winnin' and losin'. There's no such thing as honor in random matches. You can play as such to get respect points from friends, but randoms are randoms in the end. Most don't care 'bout all that. That, or they don't even realize you're intentionally playin' with honor and respect in mind.
In short, complainin' over weapon unlocks is pointless. As Tamps mentioned, it's the point of a leveling system lol.