Inflectional Simplicity

European languages have inflections: the noun, the adjective, the verb.

The Inflection of the verb is particularly called "conjugation."
For example, Latin "amo" (love) conjugates as follows (English on the right):

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amo (I love)
amas (You love)
amat (He, She, or It loves)
amamus (We love)
amatis (You [plural] love)
amant They love)
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As descendants of Latin, romance languages retain the various verb-ending.

Compared with these, one might be surprised to see how little English verb changes, only requiring "s" in the third person singular.

Indeed, what characterises the present-day English is its inflectional simplicity, which can encourages second language learners to pick up the language more smoothly and easily.
Yet, it is not necessarily so. Here is a heads-up from Baugh and Cable:   

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One must take care not to overstate the importance of this feature for second-language learners of English, as early editions of the present text perhaps did. Studies of second-language acquisition have shown, for example, that an English speaker learning German will have a mix of advantages and disadvantages . . . (10)
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It's interesting that they allude to the early editions, saying that they "perhaps overstated" the importance of inflectional simplicity. This suggest that, over time, more emphasis has been placed on the external factors rather than intrinsic value of language.

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Works Cited:
Baugh, Albert C. and Thomas Cable. A History of the English Language. 6th ed. London: Routledge, 2013.