Majors government was up against a Blair run Labour Party that was a government in waiting, there were some quality politicians in that lot. I'm pretty sure even you can see this Labour Party is not the same, if they were they would be 15-20 points in front and not losing seats in by elections.
But how did you know it was a "government in waiting" as you put it, and how do you know that the current Labour shadows aren't.....How have you come to a conclusion that they are less competent than Blair's shadow cabinet of 1995 (2 years out from a GE) for example?
I would suggest that a favourable media profile has an awful lot to do with it. Blair schmoozed the media and got them onside a long time before his election victory. The Sun in particular made a huge song and dance about it in the lead up to the 97 election. Cameron did the same when he was narrowly elected as coalition leader, and Bojo has had favourable media until very recently, but presumably he has now pissed off too many of his erstwhile chums in the industry (Max Haistings was bang on about him), among a litany of other misdemeanors. But Murdoch et al are not ready to jettison the Tory movement full stop as they are fearful of what they might lose and the scrutiny they may receive with an alternative (as with the backing of Brexit). So they are not dissing the Tories per se, just plainly unhappy with Boris. It hasn't gone unnoticed either that the Telegraph has gone into full on ERG mode in recent months as some kind of bizarre counterweight trying to claw back public opinion....
Labour on the other hand is coming out of a catastrophic lurch to the left with Corbyn, which was manna from heaven for most of the media - it made their job easy. And whilst their direction of travel is clear, they are still on that journey. Even true lefty rags like the Guardian are a bit lukewarm on Keith....probably because they went balls-deep into Corbyn at the time and fear that SKS may be another Tory-lite Blair type (which the conflicted ironically see as the most electable version of Labour).
Add in a response to a global pandemic which needs leadership and consensus on the way to tackle it (not that the government are able to provide either on their own) and maybe profile raising for political gain is not all that important right now. Let the government carry on lurching from crisis to crisis for a while longer and it does much of the hard work for them
As for the by-elections, given that all bar one of them were prior to the current recent Tory scandals, I don't think there's much to read in to them either way, but the effect of that scandal has been clear for all to see ever since. Latest opinion polls (22nd Dec) have Labour 6 points clear and as the biggest party in a hung parliament if an election were called tomorrow. Tories were in the lead up until late November. Labours inability to gain an overall majority has more to do with the collapse of their vote in Scotland since 2015 as it does with anything else - they used to typically rely on 40 seats there before that time (which would give them an overall majority in aforementioned scenario) - not any more. And lets face it, the Tories chances of forming a coalition with anyone but NI loyalists and the odd brain fart that might give us a whack-job reform MP, are slim to non-existent, so they will not be forming the next Government as things stand.....
But hey, 2 years is an awfully long time in politics
But Brexit will still be a shitshow by then
And the vast majority of households will probably be worse off to boot - never a good place for a sitting government to argue it's case from.
And as the last election result was effectively won by the least bad option, I reckon Labour will stand a much better chance in 2024