Blend some (1/4 cup or so) oatmeal into a powder. Put in 1-2 TBS peanut butter. Then add milk/yogurt/fruit/a little vanilla/some honey whatever you want. You can make your own liquid meal replacement without all the processing in commercial options, for less money and it'll be fresh.

If you want something fast but it doesn't have to be drinkable, mix 2-4 TBS peanut butter and 1/2 cup or so of oatmeal in a little bowl. Microwave for like 30 seconds to a minute or so. Add a couple TBS of juice or a small handful of chocolate chips. You've now got a basic "energy bar" that can be eaten with a spoon. Can also function as a light desert or sweet, healthy snack.

I think stuff that's churned out in huge quantities, packaged in plastic, shipped around and designed to be shelf stable is questionable at best. If microbes won't even digest it (which would make it go bad) how digestible is it for people?

Oatmeal and peanut (or other nut) butter is real food and it only takes a minute or two to mix up something basically the same as one of those replacement options, but made fresh. For my basic vitamins daily, I'll have a bowl of plain cheerios (somewhat processed but better than a pressed vitamin) and some fruit. Maybe some greens here and there. (I'll also try to hide some marmite in something, to up my B12 as I eat very little meat or dairy.)

All of these options are super cheap.