That's... the design. You have a boost clock and a sustained clock spec, and the latter is what you're guaranteed to get "under load". Usually it will do better with most parts and cooling solutions (note that the motherboard regulator hardware matters too!), but the load performance will always be "throttled".
Basically you've just misunderstood. This isn't the 90's and clocks aren't fixed things. It's impossible to treat your criticism without numbers.
As others have stated, modern Intel and AMD chips essentially boost as hard as the cooling solution will allow to eek out that last few % of performance.
Tech Ingredients has some detailed discussion in the linked video ~28:20 regarding surface preparation and paste application. (Lasers not CPUs, but the principles are the same.)