Arguments can always be made for both sides. What you've stated are facts, no denying that. However, I will present the other side of the debate with another set of facts, no less true. The reader will have to decide for him or herself which set of facts makes a more compelling case.
Big games (ICC tournaments) matter. They matter more than bilaterals. In fact bilateral performances only start to matter when they establish a pattern over a prolonged period of time.
In the last 16 years, Zimbabwe have won 2 games in major ICC tournaments (2007 vs Australia and 2022 vs Pakistan). Ireland have won more (Pakistan, Bangladesh 2x, England, West Indies). Even Netherlands has won 2 (England, South Africa). Thats two Associate nations with equal or better performance. Bear in mind they get less money, and fewer fixtures than do Zimbabwe.
In 2018 an Associate (UAE) knocked ZIM out of WC contention, and in 2022 agian an Associate did the same (Scotland). In 2022, two Associates finished ahead of Zimbabwe (Netherlands and Scotland), regardless of bilateral series results, in a tournament where Zimbabwe had home field advantage.
In all ODIs, since 2004, Zimbabwe actually have a losing record (4 wins, 5 losses) vs Netherlands and Scotland. Against Ireland its 8-8.
The game vs Scotland was massive, just like the one vs UAE. I agree. But are you sure Ballance would have tipped the balance. Sean Williams came into the game in God mode...100+ average 150 strike rate. Sole finished him. The way he was bowling Ballance stood no chance. He's a career 25 average player, and most of those were played on the highways in England. Ballance was bad luck, but what about UAE 2018? In both tournaments, even I knew Zimbabwe had sealed qualification, only to lose it at the last moment. Happens once its bad luck, twice...?