Not only is your smartphone hardware probably more powerful than DeepBlue, but chess engines are a lot more efficient nowadays (even without AlphaZero / reinforcement learning). The engines are getting better on the same hardware every year. On identical hardware, Stockfish (the top non-RL engine) is 800 Elo better today than it was 10 years ago.[1] A difference of 400 Elo corresponds to a 90% win rate for the better player (where a draw counts as half a win).

1. https://www.computerchess.org.uk/ccrl/404/cgi/compare_engine...