Why is the professional photography mode used, and the photos taken are still "unprofessional"?

Professional photography mode means that you can manually adjust more parameters instead of making photos professional.

Appendix:

Professional photography is actually very simple. As long as you master: depth of field, aperture, focal length, shutter, light ratio, large backlight, small backlight, first 45-degree light, 135-degree light, reflector, architectural light, flat light, side light, seven-point portrait, three-point portrait, full-body portrait, overhead shot, sensitivity, light ratio, off-camera flash and so on. White balance drift, metering point, evaluation metering, peripheral exposure, eye light, 18 gray, high tone, color temperature, low tone, medium gray gradient, gradient mirror, ND mirror, flash output, cutting point, horizon, multiple exposure, HDR, background blur, picture language, picture simplification, composition, anchor light, aesthetic light, crocodile. Shooting mode, mirror pre-lift, cable release, tripod, image quality, sharpness, ISO, half shutter, metering lock, CCD, white plus black minus, black and white gray, brightness value, optical zoom, digital zoom, Quan Huafu, 135 film, soft light, scattered light, strong light, gamma ray, DX format, APS-C format. Focus, shutter priority, aperture priority, AF-S ultrasonic motor lens, lens aperture ratio, B shutter, C-PL reflector, high-speed synchronous flash, ghost, internal focus, front curtain synchronization, Hou Lian synchronization, TTL, divisional exposure, splicing, sugar syrup tablet, perspective, hue, saturation, black inversion, HSB mode, RGB tricolor mode, CMYK.