Hi! Congratulations on passing your first round! So great!!!

Getting straight to your question... "Not crisp" and "not succinct" enough sounds to me like your interviewers aren't hearing a clear, confident structure in your communication. Feel free to send more information, but here are some tips for what you should practice and make sure you nail every time you structure:

1. Be MECE - This is sooo imporant for McKinsey. And if you aren't MECE and clear in your mind about the individual points and avoid points overlapping, you will inevitably complicate points, repeat points across sections, and not sound crisp. Repeating points across your tree also reduces succinctness
2. Number your points at every level - It may feel strange, but it is also an easy thing to do. So say "There are three areas I would want to looking into. First .... Second ... Third.... Now, looking at the First area of... I would want to break this down into 4 sub-sections. First subsection... Second subsection... Third subsection ... Fourth subsection.... Now, to explain the first subsection, I would want to understand ... By understanding and analysing this, I would expect to see either x or y. If i see x then it would indicate that a recommendation of z would be likely but if i see y then it would indicate that a recommendation of v would be more likely. Now looking at the second subsection...". From the interviewer (or client's perspective), this gives confidence that you are being super MECE and are really clear about each individual point (i.e. crisp!)
3. Be purposeful in every description - so the "..." should be super clear. Don't over explain, but remember to tell the interviewer (i.e. client) what they need to know. So, if you want to look at number of units sold, then say "Second, I would want to look at the number of units of beverages and food that our client sells and how that has changed over time.". When you say this, don't repeat over and over again and avoid bringing it up in a separate section (remember, be MECE)
4. Relate the lower levels of your tree back to the problem - this is a subtle but powerful way to be succinct. I find that candidates waffle when they are trying to share what they know and all their ideas, instead of directing their thoughts to the big problem. If you are always referring back to how your structure + analyses will directly answer the question, that provides a clear way to remain succinct because it has an end point, i.e. the impact to the answer

Hope this help! All the best with your final round. I am available over the next week for a session if it would be helpful to practice this with an expert and can provide more detailed feedback until you are good to go!

Best,

Yewande