They're good for staving off low blood sugar bonks. If you're not prone to hypoglycemia/low blood sugar episodes, or being hangry, you might not benefit from gels. They're mostly intended for high effort racers and riders -- more efficient than the rice cakes eaten by racers decades ago. The idea was to provide quick energy without bulk -- the latter being a problem with favored energy foods like rice and bananas. Racers and endurance riders can't always find a convenient place to poop.

The hangry thing is probably more relevant to ordinary cyclists. Blood sugar drops can diminish our judgment. We might lose concentration in traffic, neglect to check our mirrors or look over our shoulders before dodging a bit of debris. We might become irritated at a routine traffic issue that we'd normally shrug off and forget. If it persists for longer than a few moments, it's distracting us from concentrating on our surroundings or just enjoying our rides. Hangry might even lead us to confrontations over those annoyances.

The onset of low blood sugar can affect balance and strength, just enough to be an issue in traffic. Ignored it can quickly become worse.

Best way to experiment? Skip your usual meal or snack before a ride. Take something with you besides the gel pack -- a banana is good. I like the Kind bars better than most similar snack/energy bars. Ride as you usually do. If you feel a bonk coming on, use the gel pack, drink plenty of water, and continue. See how you feel every 5-10 minutes. It shouldn't be a huge difference -- we're not talking about cocaine here. For me the effect of gel packs is pretty subtle, the difference between the final 5-10 miles home feeling miserable or tolerable.