Please follow the below steps if you want to disable add to cart for a particular customer group.

Step 1: Create a plugin and define in Magemonkeys/Customerrestriction/etc/di.xml

<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xsi:noNamespaceSchemaLocation="urn:magento:framework:ObjectManager/etc/config.xsd">
    <!-- Disable Add to Cart -->
    <type name="MagentoCatalogModelProduct">
        <plugin name="IsSalablePluginAfter" type="MagemonkeysCustomerrestrictionPluginIsSalablePlugin"/>
    </type>
</config>

Step 2: Create a configuration field to select a customer group so that you can disable add to cart for that particular group in Magemonkeys/Customerrestriction/etc/adminhtml/system.xml.

<?xml version="1.0" encoding="UTF-8"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="../../../../Magento/Config/etc/system_file.xsd">
    <system>
        <section id="catalog">
            <group id="customer_group" translate="label" type="text" sortOrder="10" showInDefault="1" showInWebsite="1" showInStore="1">
                <field id="disable_cutomer_group" translate="label" type="multiselect" sortOrder="80" showInDefault="1" showInWebsite="1" showInStore="0">
                    <label>Disbale Add to Cart</label>
                    <source_model>MagemonkeysCustomerrestrictionModelConfigSourceCustomerGroup</source_model>
                    <can_be_empty>1</can_be_empty>
                    <comment>Please slect only one group</comment>
                </field>
            </group>
        </section>
    </system>
</config>

Step 3: Create a source model on this path Magemonkeys/CustomerrestrictionModel/Config/Source/Customer/Group.php

<?php
namespace MagemonkeysCustomerrestrictionModelConfigSourceCustomer;
 
class Group implements MagentoFrameworkOptionArrayInterface
{

    /**
     * @var MagentoCustomerModelResourceModelGroupCollectionFactory
     */
    private $_groupCollectionFactory;

    private $_options;

    public function __construct(MagentoCustomerModelResourceModelGroupCollectionFactory $groupCollectionFactory)
    {
        $this->_groupCollectionFactory = $groupCollectionFactory;
    }
 
    /**
     * @return array
     */
    public function toOptionArray()
    {
        if (!$this->_options) {
            $this->_options = $this->_groupCollectionFactory->create()->loadData()->toOptionArray();
        }
        return $this->_options;
    }
}

Step 4: Set default value for the disable add to cart configuration field. You have to add the below code

<?xml version="1.0"?>
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:module:Magento_Store:etc/config.xsd">
    <default>
        <catalog>
            <customer_group>
                <disable_cutomer_group>0</active>
            </wkmodule>
        </payment>
    </default>
</config>

on this path: Magemonkeys/CustomerrestrictionModel/etc/config.xml

Step 5: Now create a plugin for disable add to cart for a particular customer group :

<?php

declare(strict_types=1);

namespace MagemonkeysCustomerrestrictionPlugin;

use MagentoFrameworkAppHttpContext;
use MagentoCustomerModelContext as CustomerContext;
use MagentoFrameworkAppConfigScopeConfigInterface;
use MagentoStoreModelScopeInterface;

/**
 * Class IsSalablePlugin
 *
 * @category Plugin
 */
class IsSalablePlugin
{
    /**
     * Scope config
     *
     * @var ScopeConfigInterface
     */
    protected $scopeConfig;

    /**
     * HTTP Context
     * Customer session is not initialized yet
     *
     * @var Context
     */
    protected $context;

    /**
     * @var MagentoCustomerModelSession
     */
    protected $_customerSession;

    /**
     * SalablePlugin constructor.
     *
     * @param ScopeConfigInterface $scopeConfig ScopeConfigInterface
     * @param Context              $context     Context
     */
    public function __construct(
        ScopeConfigInterface $scopeConfig,
        MagentoCustomerModelSession $customerSession,
        Context $context
    ) {
        $this->scopeConfig = $scopeConfig;
        $this->context = $context;
        $this->_customerSession = $customerSession;
    }

    /**
     * Check if customer group for disable add to cart functionality
     *
     * @return bool
     */
    public function afterIsSalable(): bool
    {
        $groupId = $this->scopeConfig->getValue('catalog/customer_group/disable_cutomer_group',MagentoFrameworkAppConfigScopeConfigInterface::SCOPE_TYPE_DEFAULT);
        $customerGroup = $this->_customerSession->getCustomer()->getGroupId();
        if($customerGroup == $groupId)
        {
            return false;
        }
        
        return true;
    }
}

You have to follow the above steps to achieve the functionality of disabling add to cart for a particular customer group.