Referencing a solver while playing (what people call real-time assistance or RTA) is definitely a problem in online poker and is always prohibited. Solvers however play in a fairly predictable way and poker sites can detect if people are using them, though I'd imagine imperfectly. Saying that 99% of online poker is vs AIs is a hilarious overstatement.
The future of online play will be catered more toward teaching, solving, and tracking hands, rather than playing competitively for profit. I recently started a side project in Rust to do just that, mainly for love of the game and desire to learn the language.
Hoping to release later this year and perhaps productize if it gains traction.