Catching all Pokémon requires a lot of time, motivation, patience, and skills. I do have the skills to catch every Pokémon, and I have the patience as well. But time and motivation—I simply don't have. I'm extremely busy nowadays, as I have a job and am required to attend college on the side. d: I've lost all of my motivation in capturing all Pokémon five to six years ago, when playing Emerald. Pokémon Emerald was the last game that I've ever tried completing the PokéDex on. I wasn't able to get the job quite finished, but I was close. Very close. I was lacking only ten to fifteen Pokémon, and if I somehow managed to get my hands on them, I would've gotten the PokéDex done successfully. My friends advised me to use Action Replay to capture those Pokémon, but decided not to listen to them. Cheating would have made the task way too easy, and it wouldn't have given me the same feeling as doing things legitimately.
I eventually decided to give up on finishing my PokéDex. Why? Because Pokémon Diamond and Pearl were released by then, which caused me to shift my focus completely away from the goal.