>>28721904It never will be, and it's unrealistic to assume that any single game or pair of games will ever give you that.
Here's the thing, "Catching them all" has never been a central design concept of the games. It was always an optional, special goal, but it had nothing to do with the game's central single player campaign, nor does it have anything to do with the competitive side of the franchise. It WAS a component of TPCi's marketing strategy... for, like, the first couple generations. Once it broke, like, 300, they dropped that catchphrase pretty quick, and have since pivoted to focusing the marketing on themes of exploration, fostering friendships, and using the games to enrich your relationships with people.
Now, "Catching them all" IS certainly possible, but it is something that requires work, and a measure of brand loyalty. The only way to really catch them all is to follow the franchise and continue to bring your pokemon forward from Gen 3 to 4 to 5 to 6 and beyond. Someone who does not do this, frankly, does not deserve to catch them all. They did not follow the franchise in enough depth to reap the rewards.
Now, what you CAN do is go as far as you can with SuMo and no other games, and continue following the franchise from now. Within a couple games - maybe even as soon as whatever Gen 8 ends up being if you work at collecting - you'll have laid down a solid enough foundation that you can certainly "Catch them all" if that's what you really want, and by then you will have earned it.
So, from someone who is three event pokemon away from completing the current pokedex, good luck.