Magento 2.4.x has changed it's logging method several times. This guide will help you determine which you should be using for the version you are running.

Magento below version 2.4.2

$writer = new \Zend\Log\Writer\Stream(BP . '/var/log/yourlog.log');
$logger = new \Zend\Log\Logger();
$logger->addWriter($writer);
$logger->info('Your text message');

Magento 2.4.2

$writer = new \Laminas\Log\Writer\Stream(BP . '/var/log/yourlog.log');
$logger = new  \Laminas\Log\Logger();
$logger->addWriter($writer);
$logger->info('Your text message');

Magento including and after version 2.4.3

$writer = new \Zend_Log_Writer_Stream(BP . '/var/log/yourlog.log');
$logger = new \Zend_Log();
$logger->addWriter($writer);
$logger->info('Your text message');

Let's hope we get some stability now for the next few releases as this has caught me out a few times.