Web view for Android less than 6.0

Although the WebView in general works well, in which I have enabled javascript, when entering pages that require more resources, they do not load (or load poorly) on mobile phones with android versions of 5 or less. I would like to know if there is any way to work independently of the version or if, on the contrary, I should look for another alternative to work on all versions.

Code for the webView:

 /**
     * Método para la creación de la WebView, en la que se mostrará el enlace en el que el usuario deberá introducir el ID
     */
    public void CrearWeb ()
    {
        web=(WebView)findViewById(R.id.webV);

        //Habilitar JavaScript
        web.getSettings().setJavaScriptEnabled(true);
        web.loadUrl(etiqueta);
    }

    /**
     * Método para abrir el player sin salir de la aplicación
     */
    public void Seguirweb ()
    {
        web.setWebViewClient(new WebViewClient()
        {
            public boolean shouldOverrideUrlLoading(WebView view, String url)
            {
                view.loadUrl(url);
                return super.shouldOverrideUrlLoading(view, url);
            }
        });
        web.setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event)
            {
                if (event.getAction() == KeyEvent.ACTION_DOWN) {
                    switch (keyCode) {
                        case KeyEvent.KEYCODE_BACK:
                            if (web.canGoBack())
                            {
                                web.goBack();
                                return true;
                            }
                            break;
                    }
                }
                return false;
            }
        });

    }

build.gradle:

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:2.3.3'

        // NOTE: Do not place your application dependencies here; they belong
        // in the individual module build.gradle files
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

task clean(type: Delete) {
    delete rootProject.buildDir
}