Kinda. I think it's definitely true that docker is used as a distro-agnostic package manager for services, and if we only had one distro we might not need that.

It should be noted that projects like cosmo attempt to make things portable to and across BSD's as well as Linux's, so people definitely want distro agnostic packages (or a package manager), even on the BSD operating systems.

However, on the other end, docker is also powerful because it (and tools that use docker containers, like kubernetes), orchestrate services and allow people to bring them up very, very quickly. Like, to bring up a service called pairdrop, I just take this file:

***
services:
  pairdrop:
    image: lscr.io/linuxserver/pairdrop:latest
    container_name: pairdrop
    environment:
      - PUID=1000
      - PGID=1000
      - TZ=Etc/UTC
      - RATE_LIMIT=false #optional
      - WS_FALLBACK=false #optional
      - RTC_CONFIG= #optional
      - DEBUG_MODE=false #optional
    ports:
      - 3000:3000
    restart: unless-stopped

and type docker-compose up -d. And it's really quick, and arguably only possible due to the way containers are isolated and it's easy to create and destroy them. There exist solutions for automation and scripting like ansible, but they just aren't as good as the container solutions for automatically putting services up.