??? Oh yeah, says who?

protein / poutine

p[]oh teen / poo teen => both start with a p, then there's an oh or oo (which are similar) and both end the same way – disyllabic rhyme

cactus / practice ?

[]ah ck təss / []ah ck tiss => ignoring the first consonant (cluster) which anchors the rhyme and pronouncing the u as a schwa (which it is), the ck's are the same and təss and tiss are totes similar – disyllabic rhyme

skeleton / gelatin ?

trisyllabic goodness – again, the way we pronounce the on in first word is not like the on in frond but like the ən in motion (UHn) and the way we pronounce the at in the second word is not like the at in bat or cat but like the ət in … hmm, none spring to mind but it's an UHt sound here if you listen to it – sgɛ́lɪtən or ˈskelɪtən – ˈʤelətɪn – so you've k vying with g (both hard), e with e, l with l, ɪ with ə (close sounding!), t with t, ə with ɪ (close sounding!), n with n

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listen with your ears, not with your eyes

And you are right of course that gelatin and practice have the short "ee" sound at the end whereas skeleton and and cactus have the "uh" sound.

Indeed, it's an accent thing. In America at least, pronouncing "cactus" with an "is" or an "us" sound are both valid.

I think that given that the author provided a working definition, and your provided failure example is actually passing that definition (just only for the author's dialect), and given that you are now essentially trying to change the subject to "my definition of rhyme is the correct one"; well, you're just being...pedantic? argumentative? I'm not sure.