I think it's more that they came to the conclusion that the marginal benefit of someone like Ben Brereton Diaz over our current strikers was fairly limited, and did not justify the expense, but a Ramos or Gakpo (even at double the price) represented significant upgrades that would be worth it.
I'm inclined to agree. Here are all the strikers to transfer for between 12-25m (per Transfermarkt) in this past window, and what they have done:
Maupay - 1 goal in 10 PL appearances.
PEA (who wouldn't have been available owing to wages anyway) - 1 goal in 6 appearances.
Awoniyi - 3 goals in 13 appearances.
Dennis - 1 goal in 9 appearances.
Kalajdzic - 0 goals in 1 appearance (crocked).
Hwang - 0 goals in 11 appearances.
And while we're at it, those that fit the bill from the year previous:
Weghorst - 2 goals in 20 appearances (since loaned out).
Edouard - 9 goals in 41 appearances.
Alvarez - 3 goals in 12 appearances.
Ronaldo - lol.
And the year before that:
Augustin - 0 goals in 3 appearances totaling 49 minutes (he has imploded so badly in recent years that I completely forgot that Leeds bought him, for £20m assuming they keep losing court cases, until making this list).
Callum Wilson - 26 goals in 55 appearances.
Brewster - 0 goals in 27 appearances.
Karlan Grant, a player whose first name I'm including because there's a 0% chance anyone would remember him if I just wrote 'Grant', myself included - 1 goal in 21 appearances.
I count 11 strikers that moved during the past three years in that middle ground that would have been potentially available for Saints. Of those, 1 has been a success: Callum Wilson. 1 has been okayish: Edouard. Jury's still out on a couple of the signings this year, and there are at least five that have been utter calamities. The team in recent years that has done the best job of acquiring such strikers? Probably us, the more I look at it. Ings was good, and Che's decent. They're in the upper tier in terms of production.
Given that success rate, it's not damning at all to suggest that our scouting team might be unable to find a striker that is i) good, ii) in their prime years, iii) moderately-priced, and iv) wants to join Saints. Those players are exceptionally difficult to find, and more money is wasted in the pursuit of such a unicorn than just about any type of player. There are a couple names on that list -- Odd Edward and Dennis -- that I wanted at the time, but I can't say that their absence is keenly felt after seeing them in action.
If we want good strikers, history suggests that we either need to i) buy young and develop them, ii) spend a shedload of cash (still no guarantee), or iii) win the striker lottery. A lot of teams gamble on the latter, and most lose big. I can see why we weren't that interested in spinning the wheel ourselves.