Fortunately many of us stood up and made threads so changes would happen. I don’t think boosters will be an issue. I mean you can get comparable S1 weapons without Arena. Unless you really want the shoulder Xmog at 2k. Rest of gear is no requirement.
Granted the new system isn’t perfect but going with S3 reqs which is only weapon/shoulders is much better. Still start at 0 rating though which is a problem and should be 1500.
For me I’ll be doing Attunements, getting Rep so I can buy BiS from vendors and Raiding for most of my PvP BiS. There are tons of quests and items of importance outside of PvP depending on your spec. I’m sure you could BG and only do Arena but TBC offers so much more as a game and other great gear sources. Also PvE in TBC was actually fun instead of the M+ weekly vault grind Retail has become.
Also some professions have BiS weapons/items. So worth checking that out.