Unfortunately it is. These are the ownership estimates, averaged over the 3 tracking services, average review scores, average concurrent Steam players over 30 days, and Twitch viewers as of Sunday, September 28, 2:20PM UTC:
Civ5: 14M owners; 94.4% positive; 13,117 avg. concurrent players, 95 viewers over 6 streams
Civ6: 17M owners; 85.0% positive; 30,234 avg. concurrent players, 239 viewers over 25 streams
Civ7: 1.1M owners; 47.2% positive; 5,900 avg. concurrent players, 13 viewers over 7 streams
A couple of caveats here: ownership estimates vary and might include or not DLCs. If that's the case, of course older titles will show higher numbers. Civ7 was launched on consoles as well, so its ownership numbers are higher, potentially by a significant amount.
That being said, there's no question Civ7 needs an intervention of some sorts. The game simply lacks traction, both commercially and with the fan base.