So what's your point? Are you asking if you should buy skins, people's opinions, what?
If you like a skin and have extra cash, buy the skin. If you like the skin, don't have extra cash, don't buy it. Etc etc.
Ultimately skins are not worth it. I only buy skins because LoL is one of the few games I play and I have been playing it for years at this point. Skins would be more worth it if you received a physical collectors card or something honestly.
As for the updates and visual changes, as someone already stated, generally the updates only enhance the skin and I can't say I've seen one that has become worse.