There are a few things about Kodi that might help:

1. There are themes thay completely change the UI, so it doesn’t have to be outdated. I use Arctic: Zephyr – Reloaded and it is much better, though I did change the noises to something else.
2. The Jellyfin plugin works pretty seamlessly if you set up the UI correctly. I only use Kodi for Jellyfin and it acts as if it’s all local files, other than the occasional syncing notice.

However, I feel you on Netflix, YouTube, etc. - it is not ideal. I ended up either logging into a separate partition or moving to a Chromecast for those things. I’d love an all-in-one solution but I haven’t managed to find one that I’d be happy with.