Imagine ignoring legendary Roy and mythic Yune, as well as units like Spring Palla, Spring Marisa, the entire valentine's banner, the Winter banner last year, and all the other non-awakening-or-fates content. Just because most of the monthly new heroes have been beasts, (which is because that was one of the major features of the 3.0 update) even when last month was all FE6, doesn't mean this isn't the best treatment older characters that aren't just from shadow dragon (which had warriors) since cipher, and cipher is hardly an easily accessible game, and, if you were to buy packs and not just the cards you wanted, would probably become more expensive than heroes by a wide margin.

As far as new content heroes isn't dead. The summoning pool changes are meant to bridge the gap between player feedback and IS' current planning, likely to be replaced by a split pool later. That's why I haven't dismissed the game just yet. FEH players really love to focus on what we don't get and not what we do. When something the fanbase likes comes out, there's a short fanfare and people collectively go back to moaning about some other thing like powercreep skills when, realistically, these skills only get seen on the lucky or the whales and most people wouldn't inherit them anyway. The game's balance is poor, but IS tried to help with dragonflowers to patch the horrible gap in BST between the old and new units (except Haar exists and is arguably worse than Cherche, so clearly this isn't as constant as people like to say it is) and things really aren't as bad as people make them up to be.
I picked FEH up again after about 1 and a half years after dropping it after launch for technical issues, amd my launch units managed to get through the story just fine without SI (because I hadn't quite yet realised that was a thing and that my units still had defiant skills and hones)

There's my wall of text response, I really don't think things are quite that bad, even if IS does really want our money.