There is no such thing as "oversold" when Disney does not promise a set number of tickets will be sold. We as guests are at the mercy of Disney any given party because as long as they are under legal park capacity they can sell as many tickets as they want. WHEN they decide they are done selling tickets that day, they proclaim sold out and put up the sign in front. Honestly, they could proclaim every night is sold out ...
I started going to
MNSSHP in 2006, 2 parties a year, through 2015. In about 2013-14 I noticed the parties has gotten noticeably bigger the last few years. I used to go to at least one "sold out" party each year ... often a Friday but I will say most my weeknight parties were also sold out. We were still able to make it on rides with no lines (and that was before New Fantasyland was added), we could easily meet a large number of characters, we managed two bags of candy each, watched the parade, the fireworks and the stage show ... which afterwards we were able to meet the villains because they came off the stage. By 2013-14 ... it had changed. Rides had lines, sometimes no different than daytime, candy lines were longer and a few years they gave out crap for candy, characters seemed not just fewer but their sets shorter making it very difficult to do more than a couple, second parade was no longer easier to see than the first parade and I can't tell you the last time we made it to sit the front row. The saving grace was the new Hocus Pocus show - it's one of the best Disney has put together.
In 2015 I decided we weren't going at all. Other than Hocus Pocus the party had not changed since 2006. Same fireworks and same parade other than a character change on the candy float. When you add in the increasing crowds and ever increasing prices, I was having a hard time justifying going again. BUT my DS1 loves the parties so I did take him to 1 party in 2016 and 2017. Last year I got excited about the new special Haunted Mansion desserts but instead we went to several listed locations only to be told "sold out" ...........
I will be taking him again this year because it's really important to him. I have accepted we won't go on any rides because we aren't going to waste the time in lines when there is party stuff. We don't let him trick or treat at home anymore so this is his chance. When I try to justify it I just compare it to a dessert party and then YES I can well get my monies worth compared to those. If I were going for short lines and low crowds ... I wouldn't be going.
PS: Also note the first party is almost always a cluster. Not only are all the bloggers there but MANY of the CMs are BRAND NEW on the job, barely trained and for sure have no idea how to run a party. If Disney were smart those first few parties they would severely limit the tickets to let the CMs get in the groove .... but the money.