A word search is one of the few worksheets a student can complete on their first week in an English-speaking classroom. That is genuinely useful, and it is also the reason it gets overrated.
Worth separating what it does from what it looks like it does.
What it genuinely provides
A task with no comprehension floor. Almost every other worksheet in the room requires reading a direction, understanding a question, or producing a sentence. A word search requires matching letter shapes. A student who reads no English at all can start immediately and finish successfully, and finishing something on day three is not a small thing.
Orthographic exposure without pressure. English spelling is irregular in
ways that are invisible to a speaker of a phonetically written language. A
student searching for THROUGH has to hold seven letters in exact order for as
long as the search takes. That is more attention than they would give the word in
a reading passage, and it costs them nothing to be wrong along the way.
Vocabulary they can attach to something. The topics that work best here are the concrete ones. Food, the human body, weather, animals. Every word points at a thing that can be shown, pointed to, or drawn, so a student can acquire the word without needing English to define it.
What it does not provide
It does not teach meaning. A student can find all twenty words and leave knowing what none of them mean, and unless somebody attaches the meaning, that is exactly what happens.
This is the failure mode worth naming, because the sheet looks like it worked. The paper comes back complete and circled, which reads as evidence of learning in a way that a blank worksheet does not. A quiet student who finishes every word search and acquires no vocabulary can go a long time without anyone noticing.
The five minutes that make the difference
Do not hand it out cold. Read the word list aloud before the grid, holding up the object or pointing at the picture, and have the student repeat each one. Two minutes for twenty words.
The point is the sound. A student who has only seen SQUASH on paper has no
sense of it, and a student who has only heard it cannot find it in a grid. Doing
both at once is the whole reason this activity is worth their time rather than
just being something to do.
Afterward, ask for the words back. Not in a sentence and not in writing. Point at the picture and let them say it. That is the check, and it takes another two minutes.
Practical adjustments
Use a smaller grid than the age suggests. Grid size is not a measure of intelligence, and the smaller sizes on this site also run words in fewer directions, with nothing reversed. A newcomer working in a second language and a second alphabet direction does not need reversed text on top of it. The grid size guide explains what changes at each size.
Print in lowercase for beginners. The generator writes capitals by default, and the option to switch is in the print settings. Capitals are the letterform a student sees least often in a book, and for someone learning the alphabet the shapes are a separate thing to learn. Lowercase matches what they will read.
Give the same topic twice, a week apart. Generate a new layout so the grid is different but the vocabulary is the same. The second pass is where the words start to stick, and because the puzzle is visibly different, nobody experiences it as being given the same worksheet again.
Skip the idiom topics. Some lists are culturally loaded in ways that are invisible until they are not. Thanksgiving and holiday sheets carry vocabulary that assumes a shared childhood, and a student who does not have it spends the activity being reminded of that. The concrete noun topics do not have this problem.
The honest summary
For a newcomer, a word search is a low-cost way to put English spelling in front of someone who cannot yet read English, in a form they can complete without help. That is a real and specific use, and there are not many activities that do it.
It is not language instruction, and it does not become language instruction by being assigned more often. The four minutes of naming the words on either side of the puzzle are where the language part happens. The puzzle is what makes those four minutes possible.