Azure: Cannot use output from Linked Template in IF condition - azure

Question

I'm trying to deploy a Virtual network using ARM template with multiple subnets. I have a linked template which creates NSGs,route table and assigns it to a specific subnet. I'm using copy to create multiple subnets. Route table should be assigned to only one particular subnet. I control this using If condition. The issue here is i'm not able to use the linked template output in the If condition. It fails with below error.
'{
"error": {
"code": "InvalidTemplate",
"message": "Unable to process template language expressions for resource
'/subscriptions//resourceGroups//providers/Microsoft.Network/virtualNetworks/' at line '143' and column '9'. 'The provided
arguments for template language function 'if' is not valid: all arguments should be of type 'boolean'. Please see https://aka.ms/arm-template-expressions#if for usage details.'"
}
}'
Main Template (Subnet Creation snippet):-
"copy": [
{
"name": "subnets",
"count": "[length(parameters('subnetList'))]",
"input": {
"name": "[parameters('subnetList')[copyIndex('subnets')].name]",
"properties": {
"addressPrefix": "[parameters('subnetList')[copyIndex('subnets')].addressprefix]",
"networkSecurityGroup": "[if(equals(parameters('subnetList')[copyIndex('subnets')].name, 'GatewaySubnet'), json('null'), variables('nsgId'))]",
"routeTable": "[if(bool(parameters('subnetList')[copyIndex('subnets')].useRouteTable), reference('routeTableDeployment').outputs.resourceID.value, json('null'))]"
}
}
}
]
Route Table (Output snippet):-
"outputs": {
"resourceID": {
"type": "object",
"value": {
"id": "[resourceId('Microsoft.Network/routeTables', variables('routeTableName')]"
}
}
}
It works if I define a variable and pass it to if condition similar to nsg as below:-
"routeTableId": {
"id": "[resourceId('Microsoft.Network/routeTables', 'routeTableName')]"
}
"routeTable": "[if(bool(parameters('subnetList')[copyIndex('subnets')].useRouteTable), variables('routeTableId'), json('null'))]"