I will honestly say that Back 4 Blood is really fun, and offers a decent amount of replayability with how characters and card work together.

Is it better than L4D? in some aspects, yes. One of the major flaws this game has is the lack of mod support. L4D has this, thus offering a ton of user-created campaigns and all sorts of wacky mods. B4B offers a meager amount of campaigns to go through, and the fun you gain through this goes with diminishing returns. If B4B devs can somewhat provide this support in the future, I'll be looking forward to it.

Another one of its flaws is the steep price point for this game, I highly recommend you buy this game on a discounted price, not on full price. It just doesn't justify the cost at all; or you could just play it on GamePass. Playing on GamePass though will not have your progress shared on Steam FYI.

Overall it has everything has, but adding some of the modern FPS games has nowadays such as ADS and customization. It also, as I have previously said introduces a card based system in building your character, though not as in-depth as it was on its launch date as there has been changes to it, it still holds up pretty well. Partnering them up with a roster of characters with various abilities can have some really fun playstyles. Cosmetics are also present in the game, which is a nice to have since they aren't locked through some in-game purchases, though some are locked through bundles or expansion packs, but most of them you can acquire for free.

tl;dr B4B good, lacks mods to make it better than L4D, price too expensive, buy on discounted price.