Language development apps vs ChatGPT for ESL vocabulary building

Spending my prep periods this week trying to figure out what to actually recommend to my ESL students for vocabulary practice at home since parents keep asking what app to buy. I’ve used dedicated language apps in class for years, flashcard drill style, and they work fine for rote memorization but they’re boring after the first two weeks and kids stop opening them. Lately more of my students have started just asking ChatGPT to quiz them on vocabulary or explain a word ten different ways until it clicks, and honestly the engagement is way higher because its conversational and adapts to what they actually dont understand yet instead of a fixed deck of cards. My hesitation is that a general purpose chatbot isnt designed for language acquisition specifically and I dont know what its actually reinforcing versus a tool built by people who study second language acquisition. Anyone compared these seriously, dedicated apps versus just using a chatbot for vocab work?