I think a core feature of a new conlang should be that it has a systematized way to express concepts. After making my first draft of a language I decided to dig deeper into modern applied ontology. I would recommend Barry Smith's and Katherine Munn's
Applied Ontology: An Introduction. The better you understand the ontological structure of the world the better you will be able to design a language that can precisely describe the ontological structure of the world.

The result is that you really don't seem to get a lot of bang for your buck by monkeying around with your language design to try to increase the rate of information transmission.

If you have a sentence like "Four plus five is nine" that's very hard to transmit in a language like Pirahã that doesn't have a word for four but has only "one, two and many". It might be able to say two-two for four and two-two-one for five but it's really hard to express the sentence.

I think English does have cases where it's a bit like Pirahã. We have four cardinal directions and if we want to go in a 45° angle we say north-east.

Base 10 is integrated into our language in a way that we can't simply switch to base 12 or base 16 when we want to do so on a whim.

Another quite horrible case is the English word of "feel". It mixes so many different cases together. You don't have a similar distinction as between "see" and "look" for feel. Feel get's used both to thing inside your own body and outside. Láadan has:

loláad = to perceive internally, to feel a mental state or emotion, perceive with the heart (metaphorically). Passive internal feeling. "I feel sad."
lowitheláad = to feel, as if directly, another's feelings (pain/joy/ anger/grief/surprise/ etc.); to be empathetic, without the separation implied in empathy
dama = to touch, to feel with the skin. Active touching, feeling. "I am feeling the texture of the yarn." (see láad oyanan, passive touch)
náril = to feel internally, to fix your internal attention actively upon something, to-continue-to-present-time. Active internal feeling. "I am feeling angry." (see loláad, passive internal feeling)
láad oyanan = to perceive with the skin, to feel something on your skin, touch. Passive feeling. "The silk feels good to me." (see dama, active touch)

When you say "Alice is afraid of Bob", the sentence doesn't transmit whether the author is speaking about a feeling or an emotion. Modern psychology has distinct notions of feeling and emotion but it's hard to express it, because the language hasn't really caught up with it. That's again a situation where it's important to familiarize yourself with the modern ontology instead of simply copying the ontology of the existing language. Having a richer language that can express more shades of meaning is a reason for people write literature in the language instead of writing in English. Literature that also can't be easily translated back into English.