2011 MacBook Pro 13", macOS 10.12.6 Sierra, internal SATA Crucial M500 SSD, HFS+ Journaled, Encrypted boot volume:
00:00 restart tone00:08 enter FileVault password00:19 login screen...
In my tests above, the system is loaded with all sorts of software and files that have been migrated over decades. Despite that, the old Mac with the old SSD and the old macOS and all kinds of extra low-level and high-level software booted in less than 20 seconds, which is pretty good evidence that extra software and lack of "clean" installs isn't necessarily a problem if the software and hardware are well managed.In all of these boot speed tests, I don't see anyone showing that they did a 'Clean' install before running the tests. If you migrated or installed over an existing system, you may have lots of old system files (extensions, daemons, agents, old anti-virus, etc.), which will greatly affect startup times.
Also, in the immediate aftermath of a "clean" install, the system is likely to be slower, rather than faster, as macOS goes through all its gyrations of Spotlight indexing, etc.