I think that backlighting is fine only if your keyboard has switches like
Omron B3K ("ROMER-G") which had actually been designed for backlighting to begin with.
Backlighting on Cherry MX is a kludge with lots of compromises. The switch had originally been designed only to fit a two-pin LED in the
front of the key for use as an
indicator light in switches such as Caps Lock and Num Lock. The top switch housing and Cherry keycaps had been designed together so that the keycap would fit well around the switch top when pressed.
Most backlit keyboards for Cherry MX have the switches rotated 180° so that each LED is at the
back of the key, with keycaps having its legends in the top centre. Most of these keycaps have shifted symbols cramped together with the unshifted symbols so that they would be right over the LED — and that often looks like crap. Many non-English layouts have tertiary legends that often don't get backlit at all.
When these keyboards are used with other types of keycaps, because switches are mounted the wrong way round, there could be interference between a keycap and the top of the switch housing when you press a key to the bottom. So if you don't want RGB but want to use high-quality thick-walled Cherry-profile keycaps then this can happen with the home row keys.
Even some keyboards that
don't have backlighting have the switches mounted the wrong way round because they are made from some of the same parts as keyboards
with backlighting, making things worse for the rest of us.
Next, there is the issue of light bleeding out the sides under the keycaps.
When RGB backlighting was introduced,
some clone switches got a wider slit to fit an unusual wide four-pin RGB LED. Most "RGB switches" do however instead have a transparent housing with a hole over a surface-mounted RGB LED, which diffuses the light in all directions instead of just up — leading to even worse light bleed.
The only Cherry MX-
shaped switch I have seen that avoids light bleed to some degree is the Flaretech switch that is used in some of Wooting's keyboards: but those switches are optical and not pin-compatible. A Flaretech switch has an opaque housing around a clear lens that transports the light from a surface-mounted LED to the top of the housing without bleeding out the sides.