I guess that depends by what you mean with catching up - I'd say the original games are still great [I only have played bits of the campaign from Halo 1 to Reach, but I've also had played some of Halo 4 years ago in splitscreen], so the MCC is worth checking out in any sales with how you get six games in one go.

If you mean Campaign Evolved/the new remake coming for PS5, I don't have an opinion on that to be honest. I've seen videos split between enjoying the new visuals and some being turned off by the approach of how its being remade with some gameplay tweaks [like sprinting], but I never had that much of an opinion on new games and such because I don't have the budget or avenues to get my hands on those lol [which as a result means I don't have an interest in those either].

With that said, I guess it will be nice of a new introduction to Halo for PS5 players, but whether it will be up to the legend of the original Halo CE, I don't know

If you have the avenues to try out the original Halo CE and are curious enough to try it [and/or don't want to wait for Campaign Evolved lol] then I'd say that is still a valid choice, as I don't consider big remakes being a forever replacement for the original games in some cases [regardless of how much some companies pretend that it is, like forgetting about the original Silent Hill 2 while promoting the remake or the OG Resident Evil trilogy only being available on GOG while the remade trilogy are the more promoted games - RE1 at least is faithful even if different in some ways, but RE2 and RE3 remakes are NOT the same games as the OG RE2 and RE3 at all].

At the end of the day, that is up to you. Campaign Evolved probably won't be exactly 1:1 with the original gameplay and art direction but if you don't mind that [or just want to experience the Halo 1 story even if it is remade] then I guess that doesn't matter anyways. After all, if you really want to discover sooner or later the original from 2001, MCC is thankfully an option right there.