I'd say it very much does.
The focus on Snoopy itself is when the strip "jumped the shark" (here's a take, https://kotaku.com/how-snoopy-killed-peanuts-1724269473 ).
Of course Schulz dilluted it decades before the end of the strip, getting all too into repeatition and mass market concessions.
You want to feel like the subject is yours, and if it's too widespread, lots of people will learn about it, in an "inpure way" (scoff, learning about an amazing comic strip in a movie) and so it cheapens it. Only with this "hipster" view on things you could say that. I think it's impossible to cheapen something without changing it.
If the first edition was cool and the second edition changes the language for sensitivities for example, that can cheapen it, because it actually changed it. McDonald's offering a toy of a character from the first edition, changes nothing.
Only technically. In that the actual printed words wont change.
In how it's perceived in the culture, how it's read, how new readers relate to its characters, what it's seen as the start of, and so on, it does retroactively change the original.
Same how the horrendous 8th season of GoT tainted the previous seasons too. Now it's a journey to a pointless ending - and many people who haven't seen it are unwilling to get into it because they know that. Even someone rewatching the first season, now has a bad taste knowing the later plot of Danny for example, or how various things shown as prominent in the first seasons (the mysterious signs of the deathwalkers, or even the death walkers themselves) play no significant role, or are just skipped over later.
Your understanding of the events that occurred are recontextualised and your feelings are forever changed.
Perhaps we as an audience enjoyed the conceit that Schulz was writing those comics because he loved the characters and that alone.