I 100% agree that if the base you are trying to capture gets defended, and defended well, it would be much easier to move on to another field with little, to no defenders.
Here's the thing... Attacking undefended fields is about as much fun as capturing fields offline. Same thing really.
When the enemy starts pouring out at ya', and the fight get's hot and heavy, THAT is where the fun begins.
Any group of morons can take undefended field after undefended field. Takes zero strategy, skill, or know how. I chuckle often at some of the squads that are "known" for capturing bases. Put up even a slight defence, and 99% of the time they'll move on to greener pastures. I have stopped multi-wing mass squads on their squad night many a time with 1/2 or less of their numbers. If it turns into a fight, they'll go elsewhere. I guess the fighting part scares 'em.
What takes skill, team work, strategy, etc, etc, is capturing a well defended field. Pretty much all aspects of game play get represented. Buffs flying in, gv's on the ground, fighters furballin', jabo's dropin' eggs... The whole deal all in that one base capture.
Sooooo... next time you attack a field and some nme up and kill you and your mission, don't give up and move on. Head on back, and KEEP heading back until that field is yours. You might never capture it, but it's fun as heck trying. AND if you DO manage to capture it, that field take is oh so sweet, lemme tell ya'.
I can't count how many bases the WM's have captured for no other reason than we were too stubborn to quit trying.