While a middle school PTO can be anything it strives to be, I think many of us see it taking a much different - and much smaller - role than elementary school. So first, you need to really analyze what role the group should play.
You've already stated a lot of the issues. Why should the middle school continue with an emphasis on fundraising? It's a completely different environment with the kids becoming more independent. Specialty groups such as "band", "football", "choir", "science olympaid" are becoming important - often with large parent involvement (at least in the fundraising). Many, many school organizations are pursuing fundraising. The school itself may be doing fundraisers.
The structure is also vastly different in that the alliances have shifted. Before, in elementary school, everyone had their class as the anchor. So if you had 6 grades and 5 teachers each, that was 30 discrete sets of kids. Now, each child may have 6 or 7 teachers in a day. Staff has probably tripled. The kids don't align themselves with a class (Ms. Jones' kids), they align themselves with an interest. We have the band kids and the football boys and the dance team. And futher they start to identify themselves as different social subcultures (Preppy, athletes, Goth, skaters - whatever they have now...). But as PTO, you no longer have that nice, neat division of "classes" as a base structure from which to incite interest.
In my mind, the middle school PTO should definitely continue with Teacher Appreciation, enhance communication to all parents, encourage parent involvement, perhaps coordinate volunteers. Beyond that, you need to figure out what a good fit is for the organization. For instance, ours does the above, hosts the 8th grade prom (a very simple event with a budget of about $150), and helps organize volunteers for a few big things like Science Fair.
Maybe it's better to rethink its role as one of service more than money.
As I stated - you can build your PTO serve any role that works for YOUR school. But first, you have to re-examine any assumptions about what that role is and see if they are still true.
Good luck!