If you were castaway, far away from humanity and have no access to anything that can help you. Then you can employ those old methods. But so long that you can verity or have access to tools that can help you to verify, or know people who have access to the right tools that have better chance of verifying with lesser margin of error than you do. Then the guesstimate method becomes invalid.
Similarly, if you have access to time and calendar, then going outside and measuring the length of your shadow to estimate if it time for Asr is such as waste of time and may not be accurate at all.
I think the lesson the Somalis should learn from this is to leave it to those who have better tools than we do.
I second the Uluma in the West who called Eid on Saturday should come out and apologise.