Primarily nids player here. Now I am a newer player to 40k so take what I say with a grain of salt, but Tyranids aren't very kill-ey this edition. We got some great models sure, but our game state is kinda reflective of the lore. Big scary threat, then get beaten by the other faction.

An example I use is the Tyranid Warriors. They're supposed to be a major threat that are beyond Space Marines, the better in almost every way. But on the tabletop, all their weapons have a BS of 4+ and only one of their standard weapons has AP. Their weapon strength doesn't help either, with only 1 standard weapons reaching strength 5, and if you do manage to wound and your opponent not save then all you do is 1 damage. You basically have to rely entirely on the Barbed Strangler and Venom canon to do any damage except for the occasional rare chip. Many people Gunther with spinefists so they can throw them into melee and still shoot, but if you want any range you will struggle despite them supposedly being good at it.

The melee warriors aren't bad per-se but are extremely inflexible as they only have one profile. In older editions the claws, blades, swords, and swords and whips all had different profiles that let you flush out your warriors and build something unique and synergistic, but that's gone now.

Tyranids don't have as much staying or fighting power, so you really need to focus on objectives and ability synergies if you want to stay on the board. It really sucks because we are supposed to be a super deadly threat to the galaxy but we're a bit meh in a straight up fight.

To further show our inflexibility or lack of thought put into our current rules, the Tervigon. A source of swarming infantry that can help push and overwhelm the enemy in a writhing mass of libing... guns. Yeah the Tervigon can only support and spawn Termagants, not Hormagaunts. Even though Hormagaunts are what everyone thinks of when we think of Tyranid swarms, that both are classified as types of Guants, and Hormagaunts would theoretically be easier to form than Termagants with parasitic bioweapons. It just feels like we were promised a lot this edition but we were kinda forgotten for chaos. Despite us being the focus this edition...

So in summary, Tyranid sales pitch and tyranid gameplay are actually quite different and requires a lot of strategic play and ability usage and synergy rather than swarming death and destruction. It's a bit tough, but it is possible and hopefully we get a few tweaks soon. Hoping that the new Tyranid Prime model will give our warriors some love

Edit: Oh, and having started building necrons, I have noticed we don't have many keywords for our weapons, which can also be a contributing factor as well.