Asynchronous Reports with the Analytics API in Apex

asyncReport.page

<apex:page controller="AsyncReportController" readOnly="true">
  <style>
      table.reportResults { 
          width: 100%;
      }
  </style>
  
  <apex:form >
     Select Report: 
     <apex:selectList value="{!reportId}" multiselect="false" size="1">
         <apex:selectOptions value="{!availableReports}"/>
     </apex:selectList>
     
     <apex:actionPoller action="{!checkForReportResults}" id="poller" reRender="reportResults" interval="5" enabled="{!reportIsRunning}" />
     <apex:commandButton action="{!runReport}" reRender="poller,reportResults" value="Run Report"/>
  </apex:form>
  
  <apex:outputPanel id="reportResults" layout="block">
      <apex:outputText value="Running..." rendered="{!reportIsRunning}"/>
      <apex:outputPanel rendered="{!NOT(reportIsRunning)}">
         <table class="reportResults">
           <thead>
               <apex:repeat value="{!reportResults.reportMetadata.detailColumns}" var="colName">
                  <th><apex:outputText value="{!reportResults.reportExtendedMetadata.detailColumnInfo[colName].label}"/></th>
               </apex:repeat>
           </thead>
           
           <tbody>
               <apex:repeat value="{!reportResults.factMap['T!T'].rows}" var="row">
                   <tr>
                       <apex:repeat value="{!row.dataCells}" var="cell">
                           <td><apex:outputText value="{!cell.label}"/></td>
                       </apex:repeat>
                   </tr>
               </apex:repeat>
           </tbody>
         </table>
      </apex:outputPanel>
  </apex:outputPanel>

</apex:page>

AsyncReportController.cls

public with sharing class AsyncReportController {
    
    public List<SelectOption> availableReports { get; set; }
    public Id reportId { get; set; }
    public Id instanceId { get; set; }
    public Boolean reportIsRunning { get; set; }
    private transient Reports.ReportResults reportResults;
    
    public AsyncReportController() {
        availableReports = retrieveAvailableReports();
    }
    
    public List<SelectOption> retrieveAvailableReports() {
        List<SelectOption> reptOpts = new List<SelectOption>();
        for (Report r : [
             Select Id, Name
             From Report
             Where Format = 'Tabular'
             Order By Name
        ]) {
            reptOpts.add(new SelectOption(r.Id, r.Name));
        }
        return reptOpts;
    }
    
    public PageReference runReport() {
        Reports.ReportInstance reportInstance = Reports.ReportManager.runAsyncReport(reportId, true);
        instanceId = reportInstance.getId();
        processInstance(reportInstance);
        
        return null;
    }
    
    public PageReference checkForReportResults() {
        Reports.ReportInstance reportInstance = Reports.ReportManager.getReportInstance(instanceId);
        processInstance(reportInstance);
        
        return null;
    }
    
    private void processInstance(Reports.ReportInstance reportInstance) {
        reportIsRunning = reportInstance.getStatus() == 'Running' || reportInstance.getStatus() == 'New';
        if (!reportIsRunning) {
            reportResults = reportInstance.getReportResults();
        }
    }
    
    public Reports.ReportResults getReportResults() {
        return reportResults;
    }
}

This code is from my article Asynchronous Reports With the Analytics API in Apex.

I tried this but unable to get more than 2000 records :(

Please let me know any alternatives.