It is true that by following a reasonable amount of people, your own UA is proportionally distributed best to the people you follow.
Up until today, many Steemian-beginners ask for follows("follow me and I will follow you!") But that doesn't work because it adds zero benefit, and others find that irritating so as a net consequence, asking for follows results in less followers.
Also it has nothing to do with a pyramid. All that UA does, is empower real users providing awesome content and/or helping the community.
You are getting worried by over-simplifying the extremely complex follower graph that has been on Steem as long as "following accounts" is possible. There simply is no direct causal effect to increase or decrease your own UA by following or unfollowing another account, where that "rule of thumb" would apply to every account and every follow or unfollow.
PS: this is pretty technical and mathematically complex, but we've incorporated a mechanism that effectively combats an account following nobody.
Accounts that receive follows but don't follow anybody themselves, are "dangling nodes", that would lead to a division by zero problem, and or would be able to sink-in UA. We circumvented that problem by introducing a virtual account called "Omega" (or "Everybotty" as @Holger80 and myself have dubbed it). In our computations, every account virtually follows Omega, and Omega follows every account plus itself. Then we subtract Omega's UA from the matrix, and normalize all other accounts from there.
And also, we can tune the systems behavior with varying the damping factor. No worries!