Well, I do not see myself in a position to question the core design team’s decisions at all, but I can share my thoughts as a user and admin.
And being honest, I also have “Custom Horizon Mods” with more updates/changes 
I think that is the beauty of Discourse and I am here because of it. I like to personalize.
I saw the framing to offer a “simple modern theme” landed very well and also gained a lot of traction/influence to further core (including Foundation) development and features. I am with minimalism and I really like the simple digital interfaces → “less is better”.
In the meantime, I see that some of the most expected features of the theme for non-technical users who love Horizon were taken off, and I thought that perhaps they could be revisited. I also expect that because they were two real pain points while using the theme.
Meanwhile, the open-source philosophy of Discourse and this fantastic community here on Meta, plus a good harness, curiosity and ultra-focus, have given me the ability to improve the user experience on Horizon in a couple of months, and I think that is good.
There were a lot of recent changes in Discourse, and I understand there are probably too many open fronts. It is expected while we —folks who use forums like in the old days— adapt ourselves to new designs and common standards like scrolls, chats, video, drastic changes in UI/UX, and so on.
I hope my humble contributions can fill the gap and help others with the issues we faced. I am also open to contributions and/or integrations from everyone who wants to do so.
Thanks for sharing your thoughts.