Personally, I feel like gold is tough because the market is small relative to the overall economy. This makes it subject to manipulation, distortions, etc. A limited allocation can make sense, and in some cases your personal situation may have other considerations that outweigh those factors.
It's also worth remembering that gold futures have some funky rules that IMO make CME gold less that 100% trustworthy.
"Note: In the event the aforementioned calculations described in this advisory cannot be made or if CME Group staff, in its sole discretion, determines that anomalous activity yields results that are not representative of the fair value of the contract, the staff may determine an alternative settlement price."
https://www.cmegroup.com/confluence/display/EPICSANDBOX/Settlement+Disclaimer+and+Contact
"FAILURE TO DELIVER In the event a clearing member fails to fulfill its specific delivery obligations pursuant to Exchange rules, the sole obligation of the Clearing House is to pay reasonable damages proximately caused by such delivery obligation failure, in an amount which shall not exceed the difference between the delivery price of the specific commodity and the reasonable market price of such commodity at the time delivery is required according to the rules of the Exchange. The Clearing House shall not be obligated to: (1) make or accept delivery of the actual commodity; or (2) pay any damages relating to the accuracy, genuineness, completeness, or acceptableness of certificates, instruments, warehouse receipts, shipping certificates, or other similar documents; or (3) pay any damages relating to the failure or insolvency of banks, depositories, warehouses, shipping stations, or similar organizations or entities that may be involved with a delivery. © Copyright Chicago Mercantile Exchange, Inc. All rights reserved. Page 8 of 15 Notwithstanding any provision of the rules, the Clearing House has no obligation or liability to any clearing member or any other person relating to a failure to fulfill a delivery obligation unless it is notified by the clearing member that did perform, or was in a position to perform its delivery obligations, that a failure occurred, as soon as possible, but in no event later than 1 hour after the delivery deadline for the respective product, which may be extended by the Global Head of Clearing & Post-Trade Services or their designee pursuant to the provisions of Rule 702. If a clearing member does not fulfill its delivery obligations to another clearing member, it shall be responsible to the Clearing House f..."
https://www.cmegroup.com/content/dam/cmegroup/rulebook/CME/I/7/7.pdf
So if a gold bug's dream comes true and there is a run on gold, I would expect CME to just stop delivering gold and force you to settle for a paper price. Of course that price wouldn't be reflective of reality because actually buying the gold would drive the price up.