Have you used SP Flash Tool to revive a dead MTK device? Let me know in the comments—did the VCOM port show up on COM3 or COM11?
Flashing utilities must interact directly with the Preloader to modify system partitions. Because the standard Android Debug Bridge (ADB) and Fastboot protocols require a running operating system or functional secondary bootloaders, they cannot repair a severely corrupted ("bricked") device. mediatek preloader usb vcom