Many years ago I was an RWVA member/instructor.
I remember guys showing up with high dollar rifles/scopes and claiming to be very good shooters who found out they needed to brush up on the basics.
I remember guys getting so mad at their groups in the first couple of hours that they'd get up, pack up, and leave.
I remember a 10 year old girl with a 10/22 big enough she had to put the butt stock under her armpit outshooting the men on the standing position stage (remember what they say about females listening better because they don't have the male beliefs that they are just naturally good and know what they are doing already?).
I've seen guys who shot high power learn a thing or two that they told me would help them shoot higher scores.
It's fundamentals. Brushing up on the fundamentals, even for "good" shooters, can still be worthwhile.
What they teach can help you. It might take more than one Appleseed as you get a lot of info very quickly. Putting what they are teaching you into use also takes time/more practice quite often.
At that time (10 to 12 years ago) only about 15% of the attendees would shoot well enough to be awarded a Rifleman's patch at any given Appleseed. It may only be 25 meters, but it's tougher than it looks.
If you decide to go you'd do well to go to their website (RWVA) and go through the suggestions for what to bring. You'll be more comfortable with the right clothes/equipment, food/water, ammo, medicine (getting in/out of position, down on the ground, back up off the ground an uncounted number of times over the first day will leave you pretty sore and sleepy on day 2 if you don't have something to dull the pain and help you sleep.)