Captains can not legally ignore the MEL, although when an aircraft has left the stand it's deemed to have departed and the MEL may I repeat may not apply and that is where airmanship/common sense comes in.
Yes it's true that some MEL are out of date, but the answer is to update them, the company or the commander can not pick and choose which bits to apply, a classic is aircraft NAV lights in simple terms if it's a single lamp type system then the failure of a red/green/white NAV lights will deck the aircraft if it is to be flown after dark, this goes back to the days of shipping, yet modern aircraft and ships are lit up like Xmas trees with cabin lights logo lights flashing beacons & strobes and that's before you consider TCAS and a radar environment!
Globespan went down the path of selective application of the MEL in respect of EPR gauges on the 757 that went states side, no one said it was unsafe in absolute terms but like flying under the Forth road bridge, it weren't legal, we all want to keep the show on the road, but it's a slippery slope for which you'll get no thanks when the s**t hits the fan, the company will walk away from you.