Microtransactions are not inherently consumer unfriendly or a bad thing . . . as evidenced by folks upset WotC removed them from D&D Beyond.
Microtransactions have, of course, been used in a consumer unfriendly way by many video game publishers, which has led to some folks feeling that ALL microtransactions in a game are bad.
WotC has not given any reason for the removal of the a la carte microtransactions from DDB, the only speculation that really makes any sense is that this simply wasn't working for them in some way. The idea that they removed them to quiet online criticism is possible, but unlikely.
Will microtransactions return to DDB in some form, at some point? Unlikely, but who knows? Will the new VTT include microtransactions? Unlikely, but we'll see. Why would the VTT use a different marketplace model than DDB? The two services will be tied together, you won't have to purchase your books again on the VTT.
The microtransactions folks worry about for D&D . . . I think . . . are purchasing game items singly, without the option of purchasing them in a book. Like a new subclass (or feat, spell, monster) only available as a microtransaction, rather than as an a la carte option from a larger book.
Folks are nervous about pay-to-win microtransactions that gave the marketing model a bad name in the video game industry. This doesn't worry or bother me at all, as long as the game items are reasonably balanced and not over-priced. I'm fairly confident D&D isn't going to become a pay-to-win sort of game.
As usual, most of the online kvetching is sky-is-falling hyperbole. It is a bummer that the DDB Marketplace lost a la carte options, but I suspect most folks weren't using them anyway.
