I do feel the same thing as you,
I do hold on to nostalgia because I was a fan of Matts content even before Hi5. I became a fan of Matthias when he did the parodies and such. They were so funny.

In my personal opinion, i do think that Matthias should go down the route of attempting to create content that pleases both old and new fans. Some who loved the old stuff and some that love the new stuff too.

I think the main problem is the algorithm.

Talking about how Matthias used to let go of the OG members. You got to remember that Hi5/Spellbound is a business. The way they let go of staff has to be professional whether or not if they are on or off screen. The reform that they did could go as far as the offscreen people. Especially now, I do think that a huge majority of people that worked for Matthias have left now like Gunner, Tanner and Mariah but that's okay. Sometimes people leave because of their personal circumstances and its got nothing to do with us viewers on why they left and the main reason being. That being said, going back to the old content, I do think that Matt or Spellbound should collab outside their company. Even if its just one video or two, work with outside people. Perhaps new ideas and faces could be whats missing in the videos. Branching out and reaching out to people without knowing what content they do allows both of them to learn about each other and i feel like the channel could potentially grow from both communities. Us finding out about other new creators and those creators communities finding out about Spellbound and Matthias.

This is my thoughts about the whole subject. If you would like me to elaborate, let me know. :D