It seems a bunch of people are collecting sealed product so those may fit nicely.
For me they are only really good for the theme deck exclusive variants and coins, other than that it was just standard repetitive things like play mat and deck box.
It depends on your purpose for buying them. Right now they’re worth having because they’re vintage sealed product. Most people buy them now because it’s sealed and will probably not care about what’s inside since they won’t open it.
However if you want to open it and you don’t care about the exclusive stuff inside the theme deck(which is barely worth anything) then it’s not worth having.
I enjoy collecting the older theme decks, and by ‘old’ I mean WOTC era stuff. For someone like me, who would like to accumulate a sealed collection, but who cannot resist the siren call of sealed packs/boxes, theme decks are a perfect option. The temptation isn’t there since 1) I know what the contents are, and 2) those contents are underwhelming at best. Theme decks display really nice and one can’t ignore the nostalgia factor. Odds are if you were a kid in the nineties a few of the holos in your binder came from these decks lol. Good times.
If you only care about value you should buy loose packs over decks. Unless they’re the base Shadowless decks they probably won’t have much growth in comparison to packs because nobody really wants the contents. Legendary Collection is an exception because it has an exclusive Charizard and you could even lump the Rocket returns decks in the same boat.
The rest of them have little value inside them and being mass produced doesn’t help, I expect decks to be overtaken by loose unlimited packs in the future.
Otherwise, buy whatever you want. I really like the artwork on some of the ex-series and all the HGSS decks but I think the WotC era decks are ugly.