You've never been to Otakon Vegas, have you? As far as conventions go, it was a joke. I went there the year Sushio attended (2015?) . They tried to run it like Otakon despite the fraction of attendees present. They managed to piss off the wrong people, all of whom have big wallets, and its why those people never returned. I believe Otakon has given up on expanding to Vegas.
No, the game has really changed since the 'glory days' of 1998. For one thing, Anime Expo is just the anime and manga version of SDCC. It now has well over 100K attendees per year. Don't kid yourself that Hollywood isn't after the nerd dollar. It used to be that the head of guest relations would have a rolodex of contact information for Japanese guests. Take a look at the Anime Expo guest list for this year and in the past few years. Notice how many of them are brought in by companies like Aniplex, Viz, etc. The majority of guests that attend Anime Expo now are brought by the industry, controlled by the industry and, in return, Anime Expo gives them premium booth space for free. Companies like Good Smile get kick-backs from conventions like SakuraCon and Anime Expo because they bring in attendees. Lines to get into just the AX Dealer Hall for limited premium items start at least 5 hours in advance of opening, and if you want an autograph (and just one), you need to start lining up for those tickets at 11pm the night before. The tickets won't be handed out until 8 am the following morning, and if you want more than one, you need to return to the back of the line and hope that that guest still has tickets available. Anime Expo is the only anime convention I've attended where your hotel room serves as nothing more than glorified luggage storage. It also is the only anime convention I've attended where, if you actually want to enjoy the convention, you need to spend $$$ on a premium pass because you'll otherwise spend most of your time waiting in lines just to get into the panel room, even for smaller panels...but still, by and large, most anime conventions I've attended in recent years aren't all that different from when I first started going. Talking about creeps in line, or waiting to get a cel signed by a GOH, or hearing locals talk about "that annie-may stuff," - it's all things anyone who just stepped out of a 1998 convention would recognize.
Let's talk about autographs as well. That, too, has also really changed. When I first started attending conventions in 2008, you could line up for a guest and get an autograph. This largely meant that you could lounge around in the autograph area, start a line an hour or two in advance, and as long as it was orderly, staff would leave you alone. It also meant that, if you were willing to put in the time, you had a solid chance of walking away from the convention with a couple of really nice sketches for free. Now, though, in the name of 'fairness', conventions won't allow people to line up until 30 minutes prior to an autograph session. Sometimes they also implement tickets. Most conventions have cracked down on attendees getting sketches for free, usually claiming that it takes too much time and thus would be unfair to everyone (boo hoo). If the convention doesn't have an auction where they encourage you to spend big to get these sketches, the artist might have a booth in the artist alley where they will take commissions for a couple hundred each, in cash. Word has gone out that people are willing to spend a lot on artwork, and certain artists will only draw if the price is right. There also is a greater emphasis in sponsorship. I could tell stories here but I'd prefer not to make the information public.
What keeps the fan spirit alive is the size of the convention. I find that the magic number is 30,000 attendees or less. Anything after that and the convention either goes into industry overdrive like Anime Expo or half-heartedly attempts to be a convention because management realizes that they're a party con and people will just show up anyways regardless of their guest list or content, like Fanime.
I take all this into consideration when looking to attend a convention, particularly as many conventions don't announce their guests until roughly 1 month away from the beginning of the convention. It's becoming no longer an issue of what guests are showing up, but more along the lines of whether or not you can actually get something of value from them, either by waiting in line or paying for that artwork.