Is Airport Express A1392 still recommendable for access point?

I have ethernet wire to connect the access point with the main router, so I thought access point would be better than wifi repeater.

Yes.. totally don't want repeaters.

Apple designed the airports to use either wireless repeater or using ethernet as backhaul.. but the Express is the wrong unit.. an AC Extreme.. A1521 is far better for the job and you can pick them up second hand for not too many $$$.. BUT.. most are already EOL and should be replaced so it is short term alternative.

What model is the main router? If it is ISP supplied unit then chances are a mesh system is better option anyway.. only consider the Airport if you already have an airport working as main router or at least wifi already.

Really you are better considering a replacement to your wifi using modern Mesh system.

You need to be careful to pick a system that allows wired backhaul.

Depending on where you are in the world.. the TP-Link Deco series like M5 or X20 are excellent for the price and performance. Better exists but at considerably higher cost.

With Ethernet you can also use more pro systems which are not too difficult to configure.. e.g. Ubiquiti or TP-Link Omada.. but also people here are using cheap units like Xiaomi AIoT (with English Firmware) and do a great job.

100 Mbps is the top speed of the AirPort Express if it is installed as an access point or router, so that is one thing to consider.

The other is that the AirPort Express.....and other Apple routers......are long in the tooth technology and security wise. For example, the A1392 version of the Express was designed in 2011 and Apple never improved the hardware on the device. The last security update was 2 years ago.

Since Apple chose to bury the WiFi antennas inside the Express, the product will have about half of the WiFi signal range compared to other products that use an outboard antenna or antennae.

If you have an Apple router now providing your WiFi network and you want another Apple router to match, that might be a reason to consider the Express at around $20 or so if the seller will allow you to return the device if you are not satisfied.