I don’t know if it really is losing mindshare. Toki Pona is really popular among a very loud minority.
On one hand these people just may be learning it, because it’s an interesting conlang, nothing against that. Learn whatever language you like.
Then the loud part of the Toki Pona community learn it partially because they think it’s morally superior to other eurocentric conlangs like Esperanto. And those will eagerly say to you, that Toki Pona is the best language ever. So maybe is the perception that Esperanto is losing mindshare, because of Toki Pona, just a result of working propaganda by that very loud minority.
Esperanto is also in general not a very popular language, as its normally compared to English for its audacity to become a lingua franca. Still, to my knowledge it’s still the largest constructed language community. Toki Pona or other languages need to get to that level of sophistication which Esperanto already aquired during 136 years of its existence.
Even that would people contest. For me it was easier to learn and I think there things in the language, which make it easier to learn. BUT that idea that it’s truly universal “easier” is often criticized and doubted. Which leaves me with a disappointing “maybe” with a slight tilt to “it’s easier”, so “maybe it’s easier?”.
If we keep in the idea set of how Esperanto came about, then the idea was to learn two to three languages and be a world citizen afterwards. Two languages, because that would be your mother tongue and Esperanto and for three languages that would be your mother tongue, the language of your region like for cultural heritage reasons and Esperanto to be a world citizen.
I learnt Esperanto after i learnt English in school. It’s my third language and I belong to those who got afterwards more confident, that I could acquire another language by myself. So for some people it’s easier to learn and it brings them then the confidence, that when they find motivation to learn a specific new language, that they could do that.
I myself am still stuck with three languages, because I did not had a strong motivation to learn an additional language. There are too much languages and there are too much conflicting incentives to learn one over another. Wanna understand China? Learn Mandarin! Learn one of the other big languages in the world for financial progress! Then learn Spanish! Be supportive of the deaf community! Then learn one of the many dialects of sign language!