I've owned several AP's. I do not currently own one, though I will mostly likely be renewing my Universal AP at some point.
MemoryMaker - For us, Memory Maker isn't much of an incentive. We just don't get many photos, and retaining every ride photo isn't a priority for us. Even when we don't buy MM, with Magicbands we can look at them and buy them individually if we choose. for the most part, I'm happy enough with just the copious photos we take. Other than ride photos, we only had a handful of character photos. Certainly not enough photos, IMO to justify the regular price of MM for us. I'm not saying it isn't worthwhile for other folks, just not for us.
Parking - This is one AP perk we have used, but parking is included when we stay onsite, so we don't use this perk very often.
Table in Wonderland- in the past, we benefitted from buying TiW, but now it isn't worthwhile for us. If you only have two people, or don't eat many TS meals, then it is hard(er) to come out ahead buying TiW. Again, you really have to do the math. An AP alone gives you some discounts. ALSo - VERY IMPORTANT - alcohol IS included in the 2018 Dining Plan.
As another poster pointed out though, you don't have to get AP's for everyone. If you are near the break even point, then buying a single AP might make the most sense.
Either way, you are kind of betting for or against a return trip. It is kind of a gamble. Since I don't currently have an AP, I'm not locked into returning.
I also do the math carefully when considering to renew. If you only go a few times a year, the renewal 'discount' doesn't always make sense. For several years, renewing my AP's were a no-brainers. The renewal prices were quite low, and benefits were consistently great. Now, not as much.
Non WDW: It is also worth mentioning that I'm now much more open to all AP's. Whenever we go any place that charges admission, I look at the cost of an AP. Often enough, if you add up all the perks, you can come close to breaking even with a single visit. Museum AP's often include interesting newsletter subscriptions and discounts, etc. that make them worthwhile.