I think the bare ❤️ or 👍 alone, when no other reaction is available, is meaningless and could definitely be seen as diluting signal clarity. That said, I think reactions, where a much greater range of expression is available can add signal.

Zaps not only express that someone valued the content that was posted, but the magnitude of the value they found. Bit they don't express whether they found it thought provoking 🤔, funny😆, hilarious 🤣, mind-blowing 🤯, or anything else that reactions can express (💀, 🎉, 🎯, etc), and which does take a bit more effort than merely tapping on a heart icon and moving on.

Not only that, but zaps don't gave any way to express a negative reaction, such as 🤮, 👎, 😒.

So, zaps + reactions are great, but ❤️ or 👍 alone is terrible, and ❤️ or 👍 + zaps is redundant.