I have churned through three macs since 2012 and have never once installed fresh. Time machine has helped me move between them. At one point I had to temporarily move back to an old one while the other one was being fixed, and I did the exact same thing (I experienced some hiccups with brew packages that were no longer compatible due to missing CPU optimizations on the old mac).

I periodically clean my mac, though. Remove stale configuration files, cleanup apps, etc. I also have a bunch of stuff written down, as well as scripts, to help with installing new macs (to help my friends reinstall theirs).

I'm very nitpicky about configurations and apps. I've got dozens of apps and micro-apps I use. which are very modified. These include the typical BetterTouchTool, Alfred, Amphetamine, but also smaller apps like Audio Balance. My terminal is heavily customized, both in terms of iTerm 2 settings, but also in terms of my zsh config, custom commands, etc.

I'm sure I'd be able re-create my environment within days, but these would be very rough days....and time machine just works! I don't need anything else.