The simplest and fastest explanation as to why using a tiny bit of thermal paste and expecting the CPU cooler to spread it evenly does not work anymore is because over time CPUs themselves have grown bigger in dimensions.
Spreading a thermal paste: how and how much?
What Happens With Too Little Thermal Paste — Kooling Monster
Does Thermal Paste Expire: Everything You Need to Know - NabCooling
This Is Why You Should Use More Thermal Paste for Your CPU!
How to Apply Thermal Paste to a CPU? [2023 Step-by-Step Beginner Guide] — Kooling Monster
Does my computer CPU come with pre-applied thermal paste (AMD Ryzen 7)? There is a dotted gray square on the bottom, but I just want to be sure that this is the
How to Apply Thermal Paste on CPU (Easy Guide)
Is Applying CPU Thermal Paste Worth It and Mandatory? — Kooling Monster
Is thermal paste supposed to cover the whole CPU, or is it fine if it covers around 50%+ in a circle/oval fashion in the middle of the CPU? - Quora
Spreading a thermal paste: how and how much?
Thermaltake reinvents how to apply thermal paste to CPUs
What Can You Spread Thermal Paste With? — Kooling Monster
This Is Why You Should Use More Thermal Paste for Your GPU!
How to Apply Thermal Paste - iFixit Repair Guide
How to Apply Thermal Paste on CPU (Easy Guide)