French native, Esperanto and English conversational. Good notions of Italian. Notions of German (the language I’m trying to learn), Luxembourgish and Norwegian. I learnt but forgot Latin, Ancient Greek and Biblical Hebrew (I still can read them if I have a lot of time and a good dictionary).
All languages do that, yes, but as Esperanto is easier than the others, it makes it a very good first language.
I learnt English at school for almost 10 years without being able to have a discussion. I learnt Esperanto in a few months, actually used it to communicate with foreigners, and a few months after I was able to communicate in English. My English is still far from perfect, but without Esperanto I wouldn’t even be here.
Yes, you’re right that it’s a methodology problem (I’m in France), and even more right when you say that motivation is the key. It’s easier to learn a harder language if you’re motivated than an easier one but without motivation.
However, because of its regularity, Esperanto is objectively easier than all natural languages. And it’s a thing to take into account.