I still have a 2009 MBP (although was running linux for the last 5 years), I only just upgraded to a Dell XPS 13 this year.

Here's the funny thing: the keyboard started to fail after 9 years of use, this is the only thing that pushed me to finally get a PC replacement (new macs are terrible linux machines) - the little rubber domes under the keys just started cracking and breaking apart so some keys feel really squidgy - mind you they still work at least.

So there's a pretty insane statistic for you:

    - 2009 MBP = 9 years of keyboard use (my main computer)
    - 2019 MBP = <1 year before everyone has problems

Edit: RE the water thing, these models have a big sticky piece of plastic under the whole keyboard which seals it to the top case (I considered trying to replace it - although no one makes new ones so it seems kinda pointless, and quite difficult)

Just do what Apple would do and replace the entire top case. They typically run $30-$50 on eBay for older MBPs. That and a SSD upgrade (if you haven’t done that already) and you will have a functional backup computer again.

I added an SSD over half a decade ago, that's why I was absolutely fine with it's performance (at least after moving to linux and a minimal WM, OS X died for me long ago from bloat)... it's only the human interfaces that started to physically fail.

I know you can pick up spare parts for these but the problem is that they are all as old (they are commonly advertised as new on ebay, but they are not), they are used parts, and it is quite a lot of work to get all the guts out of the top case, only to replace it with a slightly less used components.

The best middle ground I could think of is to selectively replace rubber domes as they fail by cutting out the bits of silicone and gluing in new ones... only needs to pop of one key at a time.

I lost my 2009 MBP to a smaller water spill than that on the keyboard, so I don’t think there was any special design reason yours survived. Additionally, I don’t remember any special claims about those models and liquids.

It had a big plastic plane below the keyboard. Not the watertight with a drain hole type of Thinkpads, but still good enough if you're quick with turning the thing upside down.