This is fair. Something having legacy and longevity doesn't necessarily mean each individual release is a crazy seller, and recency bias is also very much a thing. Like Persona is probably more recognizable than Tales at this point. Plenty of series have died throughout the years, but many have also survived in their comfortable little cult following of getting six digit sales numbers per entry as opposed to the younger "bigger" stuff that managed to break that 7 figure gap and enter the "niche mainstream" realm. Sometimes they don't even make it to 100k like the Atelier series which has also been around since the mid 90s, and is only really starting to break out now thanks to Ryza which imo would put the franchise where Persona was after 3.I understand your point, but I don't think you should go by sales alone when judging how "big" a series is.
Splatoon shouldn't be included in this list, because while it hasn't surpassed Tales yet, I'd definitely say it's the bigger franchise. Tales has been around since the mid 90's, and it's accumulated about 20 million sales. Splatoon is five years old, and it's already past 15 million.
All that said, I still think it's ridiculous to downplay Tales legacy and influence on the genre.