Who told you that you can buy a 28 Core Intel CPU? You might be able to find a Xeon with 28 cores, at an extortionate price, but no desktop equivalent. The best desktop Intel have to offer is the 10 core Core i9-10900, and the 11th gen models stop at 4 cores.
Intel Core i5 CPUs were outclassed by last years A13 (heck, the A13 with just 2+4 cores (2 big, 4 small) gave the 12 core Ryzen 7 3900X a run for its money). This years A14 is expected to be the first CPU on 5nm, and should be faster yet. Desktop power budgets also mean they can have more cores for the non-mobile versions.