What do you mean "not delivered"? The solution to too much immigration was that Boris Johnson and the conservatives tripled immigration (and >10x'ed Pakistani immigration) because they got power through Brexit.

That's not what any reasonable person would call "not delivered".

Here is the direct source: https://www.gov.uk/government/publications/the-uks-points-ba...

(note: this was not loose enough for Johnson and with support from Rishi Sunak he loosened immigration policy even further. This was just the first shot)