Western militaries have been on the ground in Ukraine since the beginning of hostilities. Poles, Americans, Brits, Germans, French, Swedes, even Canadians... remember that Lieutenant General that was captured in Mariupol after the steel plant fell and was never seen or heard from again? The big difference between that and what is being proposed is that in almost every case those westerners have been wearing Ukrainian BDUs.
What's being proposed here is sheer lunacy, 30, 000 troops is slightly more than a division. One division on a front that stretches for nearly a thousand kilometers is going to make zero difference in the grand scheme of things, whether it's westerners on that front or whether they are replacing border guards on the Belarussian frontier.
Furthermore there's the problem of logistics and sustainment of those 30,000 troop. No one western country can even come close to what the Russians have as far as production is concerned. Even combined it's a fraction of what would be needed just to hold the lines as they are.
People need to accept that the Russians won the war already and the thing about winning wars is that when it comes time for peace talks the winner gets to dictate terms not the looser. The US cutting the Ukrainians and EU out of the negotiations, while hard to swallow, is absolutely necessary in order for Ukraine to even exist as a country in the aftermath because of they were involved no peace will be reached.
This is what happens when you allow a narrative to be spun as truth as opposed to the truth informing your narrative
