based on current lego games, i would say no, i absolutely don't think there should be a LEGO mario game. even at their best, lego games aren't as good as mario, and for the past few years lego games have been by-the-numbers, lazy reskins using the same engine as they started with 15 years ago with little to no innovation between each game. lego games haven't had any passion in them for a long time, so i don't feel confident that any lego games are really worth buying anymore, let alone a lego one
that being said, ask me the question again in a years time when the skywalker saga game has released. TT seems to have stopped their endless stream of 3 games a year seemingly in favour of giving their new star wars game more time in the oven, and although there hasn't been any substantial gameplay footage shown (as far as i'm aware, anyway), from previews and interviews it sounds like they're starting from scratch and trying to reinvent the whole thing this time, so i'm cautiously optimistic. i won't pass judgement until the game has released and we know more about it beyond PR talk, but if TT shows that they can put effort into making something new and good, then i'd be more likely to endorse a lego mario (although tbh its still not something that really needs to be made either way)