I was an athlete in the WADA whereabouts system 2010 to 2016, here's what i know. the way testing works is that the country's federation sets up a national testing pool (NTP) at the country-level. People in that testing pool have to submit a 1-hour slot and their regular activities and get tested out of competition. The issue is that for large countries like the US, someone like Elise Cranny wouldn't be in the USADA pool, while a 15:10 runner from a small country (e.g. anywhere in Europe) would be in their federation's pool. In addition, there are other tests, for example AIU, WADA top-50 international, NCAA (useless, urine only most times), and individual meets, but from what those I understand have limited and volatile funding. I competed in the NCAA DI for 4 years and never got selected for a random test, others on my team did though. It's not Cranny's fault she competes in a ridiculously deep talent pool, and it doesn't indicate dodging tests at all. Resources are limited and she wasn't top tier until last week. If anything, her saying that on record suggests that she hasn't actively thought about dodging, otherwise she wouldn't tell the world.
Someone suggested testing everyone who makes an NCAA final - that's unrealistic, count up how many athletes that would be. How do you fund that? I understand the wish for clean sports, but that's the equivalent of asking that the IRS audit every business on say a rolling 5-year-window, including entrepreneurs. They also only check big hitters (MNCs), plus random tests, because it's infeasible otherwise . You still don't go around and suspect all your local businesses of tax evasion unless they can show they've been audited. I wish it were different, but that's reality and as such it's frustrating to have discussion's like this blow up when people don't think through the implications.