My old laptop went from Windows 7 to 8 to 8.1 to 10 and then through all the 10 releases to 1901, before I wiped it and put Mint on it. No problems.
Usually doing an in-place upgrade won’t be detrimental to the health of the computer, although you should always take a backup before carrying out an updrage. (I recommend Veeam, it is free for personal use and it takes a daily incremental image of my PCs 4 hard drives and stores them on my NAS.)
Cruft can build up over time, but the really bad thing is installing more and more apps “just to try them out”. Even if you deinstall them, they leave detritus all over the place. Their registry entries won’t be removed, class associations will be broken and loading and interpreting the registry slows down. DLLs will often be left behind in the System directory, settings and temporary files in your user directories etc. Over time, as more and more programs are added (and some removed), it chokes up the system.
That Windows laptop I mentioned above, i never really installed any other software or experimented with alternative software on it. It never really slowed down - in fact, after I copied an image of the old drive to a new SSD, it had a new lease of life that kept it going for another 4 years; in fact, it felt just as fast as my Surface Pro 3, when I got that - but it was a Core i7 (no series number, the original), with 8GB RAM and the Surface Pro 3 was “only” a Core i5.
If you swap software around a lot, a clean install can be worth it. If the OS starts acting funny, a clean install can be worth it. If everything is running smoothly and it isn’t cluttered up, there is no real reason not to do an in-place upgrade.