This site has run on the vBulletin forum software for years. Probably since the beginning. There was so much integration with the customization for the gallery and other functionality that is not a standard feature of vBulletin. I'm sure that is why they stuck with vBulletin when they did the site redesign. They are talking about moving to PHP 8 which is a different company and a different product. That will require more work than the last redesign. Drummerworld and DFO are on XenForo.
The speed thing is a massive problem and they need to fix that as quickly as possible. That will kill this site quicker than any gripes about the site layout.
These different software packages have different costs. These costs are just one factor. The second cost is the customizations that they will surely want to keep. The third cost is the work to move the site to a different software. There will be other costs if they have to bring in any other people to help with the switchover, to help troubleshoot, ect.
On a daily basis, there is the running of the site. This is Tommy and crew, which aren't getting paid for this. Then there is any outside help they may be paying for to do IT administration.
In addition, there is a monthly cost for hosting the site.
My point is, this is a lot harder than it looks. And a lot more expensive. I know there are things people aren't happy with the new site, and the intermittent slowness is a huge problem, but instead of complaining and threatening to go away, how about asking Tommy, what you can do to help? Maybe kick in a few $$ to help defray all of the costs to run this site.
The old site is never coming back so everyone really needs to get over that. Frankly, I found the old site atrocious because of the limitations of the old version of vBulletin it was running on, so the new version is a huge step up.
Let's try to be part of the solution rather than complaining about everything we don't like. The bottom line is, this is the best site for information on vintage drums out there. Complaining won't fix anything. Offering Tommy and crew help, will.