APFS Is Not Optional (apple.com)
From a new Apple knowledge base article: When you upgrade to macOS High Sierra, systems with all flash storage configurations are converted automatically. Systems with hard disk drives (HDD) and Fusion drives won't be converted to APFS. You can't opt-out of the transition to APFS.
Mac products a few years ago.
Linus agrees with me. From the Wikipedia page for HFS+:
HFS Plus lacks several features considered staples of modern file systems like ZFS and NTFS. Data checksums is the most routinely cited missing feature. Additionally, the core of the filesystem uses case-insensitive NFD Unicode strings, which led Linus Torvalds to say that "HFS+ is probably the worst file-system ever."
Linus can blow me.
Let him stick to his toy, Unix-wannabe, pseudo-OS.