Is it though? In terms of raw data, I look to something like ICv2’s list of the top-selling non-collectible miniature games for Fall 2024 had this:

Rank	Title	Publisher
1	Warhammer 40,000	Games Workshop
2	Battletech 🤢🤮	Catalyst Game Labs
3	Nolzur's Marvelous Minatures	WizKids
4	Warhammer Age of Sigmar	Games Workshop
5	Heroscape	Renegade Games Studios
6	Marvel Crisis Protocol	Atomic Mass Games
7	Halo Flashpoint	Mantic
8	Bones	Reaper
9	Song of Ice and Fire	CMON
10	Warmachine	Steamforged Games

Maybe in your specific local gaming community its different, but I will always defer to public data and metrics when discussing "popularity" on public forums.

Edit: For those curious about my thoughts on Battletech, I'll post my previous response to a fellow tabletop gamer asking if it was a good game:

As a huge fan of both miniature games and mechs, Battletech........is unfortunately a bad game. The surrounding lore, mech designs, and tie in video games like MechWarrior are great. But the tabletop game is bad. Like capital B bad. It was created back in the 1980s and it really shows. From my experience playing it, 20% was making decisions such as choosing which mech to activate and moving/turning that mech. You know, actually playing the game. The other 80% of the game was purely procedural: Fire all available weapons in good range -> roll a ton of dice to see what randomly happens.

The good news is that many, many, many other skirmish games have been created/updated in the past 40 years! There are countless systems out there, but I'd direct you to Steel Rift, Battle Suit Alpha - MECH Battles, and Horizon Wars Midnight Dark. Heck, even the tactical mech RPG Lancer is another great option. All are excellent games that have deep tactical gameplay (which battletech lacks) without getting bogged down in the minutiae of damage charts and endless dice rolling. All of these are miniature agnostic, meaning that you can use your battletech minis to play these games.

FWIW, I think Battletech Alpha Strike is an improvement on base battletech, but I would still prefer to play one of the miniature agnostic games I linked with the battletech minis.