That fight was very winnable if you followed up when Ali went in TBH no matter if Garen was TPing in or not. Even if you traded kills Ali for Garen you just traded a support for a top laner which is a win and with Anvia having blue buff + Veigar + you having your ults your team fight is better then theirs, baron or not that was not a bad call to go in on and fight instead of letting them siege with baron and you losing top inhib again.