I disagree with I guess everyone here and would like to present some counterpoints. I think guard reserves are fantastic. For almost everyone, holding on to resources before guard reserves came out was so hard because it was virtually impossible to defend against any decent attack. Now you actually can. In addition, I regularly attack (and beat) bases with guard reserves, I just have to plan even more carefully, get shields down then use airstrikes et cet. To me its more fun than brainlessly winning every attack. Does it slow down your attacks to have to use aircraft...yes, but aircraft SHOULD be used, that's why they are in the game!
Maybe a solution would be for the devs to cut the time it takes to train the air support so that your attacks are not so time-constrianed? I don't feel its unfair in any way that in order to crack a really well-defended base that you need to use your squad reserves, your air support, and your droideka(s).
On the other hand, I'd also note that I find only about 20% of bases I scout even have guard reserves equipped, so it's quite easy to avoid them entirely(at least in this stage of the game).