Restaurant vegetables taste completely different from mine and I cannot work out what they are doing

Adding the preparation half, which decides how much water you brought to the fight.

Dry everything. Washed vegetables carry a lot of surface water and every drop has to boil off before browning can start. A tea towel or a spin in a salad spinner is thirty seconds and it changes the result.

Cut evenly, and not too small. Uneven pieces mean some are burnt while others are raw, which pushes people to lower the heat. Slightly larger pieces survive high heat better.

Salt at the right moment. Salt draws water out. Salting well before cooking gives you a wetter pan; salting at the end or once browning has started avoids that. For roasting it matters less; for a hot pan it matters.

Do not stir constantly. Contact time is what browns. Put things down, leave them alone for a minute or two, then move them. Continuous stirring keeps everything just below the temperature where anything interesting happens.

Use enough fat. Fat conducts heat into the surface. A dry pan browns unevenly and sticks, and people then add more vegetables to stop the sticking, which makes it worse.

And if the pan is genuinely full and you cannot batch - put it in a hot oven instead. Roasting works fine at volume and the mechanism is the same.

Two things, and they are the same thing seen from different sides: your pan is too crowded and not hot enough.

What happens when you put a lot of vegetables into a moderately hot pan: they release water, the water cannot evaporate fast enough because there is too much of it and not enough heat, the temperature in the pan drops below where browning happens, and everything sits in its own steam. Pale, soggy, steamed-tasting - exactly what you described.

What a restaurant does differently is not an ingredient:

Much more heat. Restaurant burners are enormously more powerful, so the pan recovers instantly when food goes in. At home you cannot match that, so you have to compensate the other way.

Much less in the pan at once. They cook in small batches, constantly. This is the compensation available to you and it is the single biggest change.

A properly preheated pan. Hot before anything goes in, not warming up with the food.

So: heat the pan properly, cook half as much at a time, and accept two batches. Same ingredients, same oil, and it is a different dish. That one change accounts for most of the gap.

The thing that stops most home cooks fixing this: the heat you need feels wrong.

People have been told not to burn things, so the instinct is medium. Browning happens at temperatures that look alarming: the pan will smoke a little, it will be loud, and it will feel like it is about to go wrong. That is the correct condition and it is what nobody demonstrates at home.

A few things that make committing to it easier:

Use a pan that can take it. Carbon steel, cast iron or heavy stainless. A thin nonstick pan cannot go where you need to go and should not be asked to.

Have everything ready before you start. At high heat there is no time to chop, and this is why restaurants prepare everything first. That habit is more of the secret than any technique.

Use an oil with a high smoke point for the searing part, and add butter at the end for flavour if you want it.

Extractor on, window open. It will smoke and that is expected.

And finish the way a restaurant does: something acidic at the end, lemon, vinegar: off the heat. Browned vegetables with a squeeze of acid taste finished, and its absence is the other half of why home versions taste flat.