I'm not exactly sure where you're going with this... If you're saying for some reason marketing the newest Pokemon to come out is somehow not a good idea, then that really makes no sense. If it's a prominent Pokemon in that generation or time period, it's going to be marketed. That's how things have been for years now, it's always been the prominent Pokemon of that time.
It's also worth noting that TPC is a company who sells products for profit. I'm pretty sure they're putting out what's most marketable. That's why there's so many eeveelution products, as those are popular and because people know Let's Go is coming out, they can identify it. They're putting out Legendaries often because it's their campaign this year, the Legendary Pokemon thing. It's the same idea as how in 2016, being the 20th anniversary, they had their 20th campaign. And of course, with things like the Island Guardians, Solgaleo, Lunala, Ultra Beasts, etc. being so much a part of gen 7, there's a lot of gen 7 product. It's the clear choice that they would put out products that would appeal to the hype they're drumming out.
And it's not that they hate "regular" pokemon either--There's marketing and merchandising and even TCG products for nearly everything, ESPECIALLY these days. Even in our main sets, despite not being heavily promoted, more and more obscure Pokemon are being given love as ultra rares-It hasn't been at this level since the ex era over ten years ago now.
I guess, in short, I wouldn't consider these days to be leaving many things in the dust. Sure, there's neglected Pokemon but it would be WAY too much for them to give everyone the same amount of attention. I'd say we're at a greater balance than ever before, between the popular AND the obscure.
