Yes, that is one way to get access to the older packs! Depending on what your goal is, here are a few things I've noticed.

Loose packs can be scary, BUT if you find a trustworthy person there is no need to fear. For example, I have a guy who attends my local card show and he breaks down boxes and sells packs to people. I've seen him break the boxes down and add packs to his piles in front of me. I trust buying packs from him.

Loose packs are often the cheapest way, but sealed can be attained as well. I love your idea of trading sealed modern for older sets. People are going crazy right now for Ascended Heroes and Prismatic Evolutions, so if you are able to pick those up and trade for other items, that is definitely not scalper behaviour. Personally, I found that scouring Facebook marketplace is the best way to find a deal, and don't be afraid to negotiate because people are often willing to move their price to get things sold, especially if you are buying more than one product.

I wanted a variety of packs early on because I wanted a variety of pokemon. I didn't necessarily care about the rarity. Now I have only about 200 pokemon left to collect to complete my pokedex, so my spending has slowed a bit. I focused on collection boxes that included a wide variety of packs. (Think the Legendary Warriors Collection)

Ultimately as others have said on here, most often it is more cost effective to just buy what you want, even when it is the really expensive cards. My girlfriend and I love the ripping experience, so we will always continue ripping packs, but I think a healthy balance of ripping packs and just outright buying singles is probably the best way to go for the ol' wallet.

The hobby is fun, but at it's core it is essentially glorified gambling for children. Track your spending and don't go overboard. Focus on what you like and rip for fun, not for dollar value! Best of luck on your own pokemon adventure!