What you are seeing is real in a lot of cases, just not as black and white as "post more = lower engagement". In most cases, its a content dilution + audience fatigue + quality decay across each post that is causing problems and NOT a penalty from the algorithm.
Therefore, when there is an increase in the number of posts (especially between ~3 -- 5-7+ times/week), it usually leads to:
This is the point when you have your most average content quality because production pressure rises.
Not every post gets attention, the audience doesn’t have time for it, so engagement is “splitting”
Each individual post is then distributed by Instagram according to early engagement signals — weaker early performance can limit reach.
However, there is another side to the coin: accounts that post less frequently seem to put much more effort into every post leading to stronger hooks and retention leads higher saves/shares and as a result comes higher engagement rate.
Low-frequencyposting can work better for you, high frequency posting can do the same, if:
Content value is relatively uniform (by series format, reels structure, strong hooks)
Frequency can be absorbed because the audience is large enough
You Are Not Repeating or Getting Too Close to the Same Type of Content
This means that it’s not posting more makes your engagement go down by default, it simply reveals poor consistency faster. What matters is not the amount of posts, but the content quality par post and posting pressure exercised.