There are also stage 1 and stage 2 GXes you know...
Way back in the days of the base set the most dominant archetype (Haymaker) doesn't evolve at all, instead capitalizing on basics with high HP, respectable attack costs and power. Sounds familiar?
Also banning EX/GX is not the answer. Those Greninjas and Rainbow Roads will still laugh at you. Btw Lugia EX, while good in the past, is now an obsolete EX due to the presence of Tapu Lele GX which has pretty much the same attack but has a very good ability as well.
The modes do not focus on EX/GX. It is true that pretty much any meta deck will have at least one GX (probably Lele if nothing else), but there is a reason why those EX/GX are played. For a card to be playable, it needs to have one or more of these attributes:
1. Deal lots of damage for respectable energy cost. Many cards in PTCG lack this. Most do too little damage for the energy cost required while some like Charizard GX have the damage but have a steep energy cost that's too difficult to pay for.
2. Able to withstand massive hits, and contribute something meaningful to the team. Lunala is a bad GX even though it has bulk cuz it doesn't contribute enough for a stage 2, as its attack is too weak and its ability is insufficient support for a stage 2. Meanwhile, Wailord EX, who has the same amount of HP, is a basic (thus far easier to get out compared to Lunala GX), and is part of an annoying archetype of stall decks.
3. Able to offer sufficient support to the team. E.g. Magnezone can accelerate metal energies quickly to Dusk Mane Necrozma GX to pay for its costly Meteor Tempest attack which has OHKO potential. Tapu Lele GX can search the deck for a supporter. Oranguru/Octillery can draw extra cards. Meanwhile, Alolan Sandslash with Slush Rush, though it draws cards as well, draws too little (only one card compared to up to 5 for octillery), thus it offers very little support and thus not worth playing.
4. Have some special trait that makes them worth playing against the meta. E.g. Alolan Ninetales and Hoopa for their immunity to EX/GX. Mewtwo/Mew EX can hit Buzzvole GX (a popular meta card) for weakness.
Every pokemon card in the meta has at least one of these traits. The majority of cards in PTCG simply lack any sort of trait that makes them worth playing over the meta cards.
I recommend you take a look at Greninja BREAK. No other meta deck evolves as much as it does. Yet it is potentially far more annoying to face than any GX deck.