>>36002624The challenge in both main series and PMD come in their postgame, whether it be the Battle Frontier for main series, or Zero Isle and the Level 1 dungeons in PMD. The main storyline for both games are rather simple to tackle, both requiring rather simplistic strategies. In main series' case, the best strategy is to use high BP moves, while PMD's strategy is to plow through dungeons, and use items on bosses. Primal Dialga? Stun Seed it, use Violent Seeds to buff your main duo, throw a Vile Seed and have away at it. Champion Blue? Use the Game Corner TMs. Both games give you more than enough leeway to get by with your favorites, even if it's an uphill battle at first. Optimization for both games come in how you use items and moves, you're rarely limited in what you have to catch in main series, or what starters you have to pick in PMD.
The challenging modes of main series and PMD alike are more restrictive in what you can use, but they are not impossible. Destiny Tower is best completed with a female Drifblim, with many other Pokemon having trouble with it. However, beating it is doable with just about anyone, except it requires much more strategy and luck. (Recently, someone managed to complete Destiny Tower with a Caterpie.) In a similar manner, you'll have a much easier time beating the Battle Frontier with a specialized team, but it's still entirely doable with a few favorites and a lot of luck.
The argument that main series has a meta? It's completely narrow-minded, since the games' single player is created in a way where almost any Pokemon can win. If PMD had multiplayer PvP, you'd be hard-pressed to find a team that wasn't 4 female Drifblim with Ominous Wind and Silver Wind linked together.